Non-absorptive electro-optical glazing structure employing composite infrared reflective polarizing filter

ABSTRACT

An electro-optical glazing structure having reflection and transparent modes of operation for selectively reflecting and transmitting electromagnetic radiation without absorption, respectively. The electro-optical glazing structure comprising: an electro-optical panel having first and second optical states of operation; a composite broad-band infrared (IR) reflective polarizing filter structure of electrically-passive construction, mounted to the electro-optical panel; and an optical state switching mechanism for switching the electro-optical panel to the first optical state of operation in order to induce the electro-optical glazing structure into the reflection mode of operation, and for switching the electro-optical panel to the second optical state of operation in order to induce the electro-optical glazing structure into the transparent mode of operation. When the electro-optical panel is switched to the first optical state of operation, electromagnetic radiation within a first prespecified bandwidth falling incident upon the electro-optical panel is reflected from the electro-optical panel without absorption. When the electro-optical panel is switched to the second optical state of operation, electromagnetic radiation within a second prespecified bandwidth falling incident upon the electro-optical panel is transmitted through the electro-optical panel without absorption. By virtue of the present invention, the glazing structure is capable of providing both thermal insulation as well as privacy functions.

RELATED CASES

This is a Continuation-in-part of: application Ser. No. 08/805,603entitled “Electro-optical Glazing Structures Having Total-reflection AndTransparent Modes Of Operation For Use In Dynamical Control OfElectromagnetic Radiation ” filed Feb. 26, 1997, now U.S. Pat. No.5,940,150 application Ser. No. 08/739,467 entitled “Super BroadbandReflective Circularly Polarizing Material And Method Of Fabricating AndUsing Same In Diverse Applications”, by Sadeg M. Faris and Le Li filedOct. 29, 1996, now U.S. Pat. No. 6,034,753, which is aContinuation-in-Part of application Ser. No. 08/550,022 entitled “SingleLayer Reflective Super Broadband Circular Polarizer and Method ofFabrication Therefor” by Sadeg M. Faris and Le Li filed Oct. 30, 1995,now U.S. Pat. No. 5,691,789; application Ser. No. 08/787,282 entitled“Cholesteric Liquid Crystal Inks” by Sadeg M. Faris filed Jan. 24, 1997Now U.S. Pat. No. 6,338,807, which is a Continuation of application Ser.No. 08/265,949 filed Jun. 2, 1994, now U.S. Pat. No. 5,599,412, which isa Divisional of application Ser. No. 07/798,881 entitled “CholestericLiquid Crystal Inks” by Sadeg M. Faris filed Nov. 27, 1991, now U.S.Pat. No. 5,364,557; application Ser. No. 08/715,314 entitledHigh-Brightness Color Liquid Crystal Display Panel Employing SystemicLight Recycling And Methods And Apparatus For Manufacturing The Same” bySadeg Faris filed Sep. 16, 1996 now U.S. Pat. No. 6,188,460; andapplication Ser. No. 08/743,293 entitled “Liquid Crystal Film StructuresWith Phase-Retardation Surface Regions Formed Therein And Methods OfFabricating The Same” by Sadeg Faris filed Nov. 4, 1996 now U.S. Pat.No. 6,133,980; each said Application being commonly owned by Reveo, Inc,and incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of Invention

The present invention relates generally to an electro-optical glazingstructure having total-reflection and semi-transparent andtotally-transparent modes of operation which are electrically-switchablefor use in dynamically controlling electromagnetic radiation flow indiverse applications.

2. Brief Description of the Prior Art

The use of windows in homes, commercial buildings, and automotivevehicles alike is very well known. The reasons for providing windows insuch structures and systems are directly related to the functions theyperform. For example, window structures provide for ventilation,lighting, a sense of spaciousness, as well as a way of making contactwith the outdoors. Windows made of glazing (e.g. glass material) alsopermit selective transmission of electromagnetic radiation between theoutdoors and the interior space of homes, commercial buildings, andautomotive vehicles. While conventional forms of glazing serves manyuseful functions, such forms are not without problems.

An appreciation of the problems presented by the use of conventionalglazing in windows, can be most easily attained by recognizing thenature and composition of electromagnetic radiation with which windowsuniversally come in contact.

On a clear day at sea level, electromagnetic radiation is composed of 3%ultraviolet light (i.e. electromagnetic radiation in the UV band), 44%visible light (i.e. electromagnetic radiation in the visible band), and53% infrared light (i.e. electromagnetic radiation in the IR band). Inaccordance with the laws of physics, 50% of all electromagneticradiation produced is left hand circularly polarized (LHCP) while theother 50% thereof is right hand circularly polarized (RHCP). The totalelectromagnetic radiation striking a window surface is a combination ofdirect radiation from the Sun and diffuse radiation from the ambientenvironment. While electromagnetic radiation is broad-band in nature, itis the ultraviolet light component thereof which causes moleculardecomposition in various types of plastic material and inorganic dyes,which results in color fading.

When electromagnetic radiation strikes a glass window, three differentphysical processes occur. Some of the radiant energy is transmittedthrough the glass; some of the radiant energy is reflected off theglass; and a small portion of the radiant energy is absorbed by theglass. The energy transmitted through the glass window is typicallyabsorbed by furnishings or structures within the interior environment,and often becomes trapped therewithin causing an increase in interiortemperature.

Depending on the season, electromagnetic radiation transmitted throughglass windows can be either mitigate or worsen the thermal loadingimposed upon the heating and cooling systems associated with the glasswindows. Consequently, during the hot weather season, it is highlydesired to shield windows and sliding glass doors from electromagneticradiation in order to lessen thermal loading upon cooling systems.During cold weather season, it is highly desired to expose windows andsliding glass doors to electromagnetic radiation in order to lessenthermal loading on heating systems.

In short, it is highly desired to selectively control the transmissionof electromagnetic radiation through window structures at differenttimes of the day and year so that thermal loading upon the heating andcooling systems of residential, commercial and industrial buildingenvironments can be minimized. By minimizing such thermal loading, powercan be used in an economical manner to control the internal temperatureof residential, commercial and industrial building environments.Achievement of this goal would impact the natural environment in apositive manner, while improving the quality of life.

With such objectives in mind, great effort has been expended in recenttimes to improve the ways and means of selectively controlling thetransmission of electromagnetic radiation through window structures.

One approach to electromagnetic radiation control involves using awindow shade to reduce the transmission of electromagnetic radiationthrough windows. The most popular type of shade is the window blind.However, as window blind is mounted within the interior of the buildingor transportation environment, electromagnetic radiation is allowedtransmit through the window, raise the temperature within the internalenvironment, and thus increase thermal loading on cooling systems duringthe hot weather season. Also, the operation of window blinds requiresmechanical or electro-mechanical controls which tend to be bulky andexpensive to manufacture, install and maintain.

Another approach to electromagnetic radiation control involves the useof sun control films which are physically applied to the surface ofglass windows in building and automotive vehicles alike. Presently avariety of different types of sun control film are marketed by variousfirms. Such electromagnetic control films can be categorized into one ofthe three basic categories, namely: high reflectivity film; heat savingor winter film; and fade protection film.

High reflectivity electromagnetic films are most effective at blockingsummer heat. The higher the reflectivity of electromagnetic film, themore effective it will be at blocking electromagnetic radiation.Electromagnetic reflectivity film having a silver, mirror-like surfaceis more effective in blocking electromagnetic radiation than thecolored, more transparent films. Electromagnetic reflectivity films canlower the U-value of glass by more than 10%. Notably, in climates havinglong heating seasons, the use of high reflectivity film prevents usingthe winter sun to warm the interior of buildings during the cold weatherseason, and thus lessen thermal loading on building heating systems.

Heat-saving or winter films are designed to reduce winter heat lossesthrough glazing. These films can lower the U-value of glass windows bymore than 20%.

Fade-protection films are designed to filter out ultraviolet rays.Ultraviolet rays cause about 60-65% of color fading in most homefurnishing fabrics and automobile dash boards.

While electromagnetic radiation control films of the types describedabove can be used to control heat and glare, eliminate sun damage, andto a lesser extent, reduce visibility into buildings during the daytime.The major disadvantages thereof are reduction in interior light, loss ofvisibility, and extra care required in cleaning. Moreover, prior artelectromagnetic window films are incapable of changing from transmissiveduring winter months to reflective during summer months in order toeffectively use electromagnetic radiation for dynamic temperaturecontrol of biological environments (e.g. human habitats, greenhouses andthe like).

An alternative approach to electromagnetic radiation control involvesusing special glass panels having radiation transmission characteristicswhich effectively absorb (i.e. block) the infrared and ultra violetwavelengths, while transmitting the visible wavelengths thereby allowingwindow viewing and day light to enter the interior spaces of buildingsusing such window technology. While the light transmissioncharacteristics of such glass provides a measure of electromagneticradiation control during cooling seasons, where outdoor temperaturestend to be above 72 degrees Fahrenheit, its IR absorptioncharacteristics prevents, during heating season, IR wavelengths of Sunlight to warm the interior spaces of building structures in which suchglass panels are installed. Consequently, during heating seasons, suchglass fails to lessen the thermal loading on the heating systems of suchbuildings, as would be desired in an effort to conserve energy andheating resources during the winter months.

In recent times, there has been great interest in using variable lighttransmission glass or glazing, referred to as “smart windows”, toachieve electromagnetic radiation (i.e. energy) control in buildings andvehicles alike. The reason for using smart window structures, ratherthan conventional glass window panels, is quite clear. Smart windowstructures have light transmission characteristics that can beelectrically controlled during the course of the day (or year) in orderto meet lighting needs, minimize thermal load on heating and/or coolingsystems, and provide privacy within the interior spaces of buildings andvehicles alike.

The use of chromogenic switchable glazing or smart windows forcontrolling the flow of light and heat into and out of a glazingaccording to occupant comfort, is discussed in great detail in thefollowing papers: “Chromogenic Switchable Glazing: Towards theDevelopment of the Smart Window” by Carl Lempert published in the June1995 Proceedings of the Window Innovation Conference, Toronto, Canada;and “Optical Switching Technology for Glazings” by Carl Lempertpublished in Thin Solid Films, Volume 236, 1993, pages 6-13, bothincorporated herein by reference.

In general, there are several different types chromogenic switchableglazing or smart windows, namely: non-electrically activated switchableglazings; and electrically-activated switchable glazings. Thenon-electrically activated types of chromogenic switchable glazing arebased on: photochromics, thermochromics and thermotropics. The mostcommon electrically-activated types of chromogenic switchable glazingare based on polymer dispersed liquid crystals (PDLC), dispersedparticle systems (DPS), and electrochromics.

Prior art smart window structures based upon conventional twistednematic (TN) or super twist nematic (STN) liquid crystal technologyrequire the use of a pair of polarizers. This, however, results in highoptical loss, as up to 60% of the incident light is absorbed by thepolarizers, in the desired non-blocking mode of operation.

While a smart window structure based on polymer dispersed liquid crystal(PDLC) technology offers better performance than TN or STN based windowstructures, such smart window structures suffer from several significantshortcomings. In particular, conventional PDLC panels have a translucentstate which can be used only to provide privacy, but lack a totallyopaque state and a totally reflective state required for electromagneticradiation control functions. In addition, the viewing haze limitationprovided by the PDLC panels prevents clear viewing through this priorart window structure at larger viewing angles.

A primary drawback associated with Dispersed Particle Systems is thatsuch systems simply do not have a reflection mode of operation, and thuscreated heat build-up within interior spaces which is sought to beavoided in thermal radiation control applications.

Thus it is clear that there is a great need in the art for an improvedform of variable light transmission glazing structure which avoids theshortcomings and drawbacks of prior art technologies.

DISCLOSURE OF THE INVENTION

Accordingly, a primary object of the present invention is to provide anelectro-optical glazing structure which avoids the shortcomings anddrawbacks of prior art technologies.

Another object of the present invention is to provide an electro-opticalglazing structure which has total-reflection, semi-transparent andtotally transparent modes of operation for improved control over theflow of electromagnetic radiation within the solar region of theelectromagnetic spectrum (i.e. Solar Spectrum).

A further object of the present invention is to provide such anelectro-optical glazing structure, in which the modes of operation canbe electrically-activated or switched, while avoiding the use of energyabsorbing mechanisms.

A further object of the present invention is to provide such anelectro-optical glazing structure having a broad band of operation,including the IR, visible and UV portions of the electromagneticspectrum.

A further object of the present invention is to provide anelectro-optical glazing structure, comprising an electrically-activeπ-phase retardation panel interposed between a pair ofelectrically-passive electromagnetic radiation polarizing panels, bothof which are capable of reflecting electromagnetic radiation of acertain polarization state, whereby a totally reflective state ofoperation and a semi-transparent state of operation are provided overthe electromagnetic region of the electromagnetic spectrum.

A further object of the present invention is to provide anelectro-optical glazing structure, comprising an electrically-activeπ-phase retardation panel interposed between a pair ofelectrically-passive electromagnetic radiation polarizing panels, bothof which are capable of reflecting electromagnetic radiation of a linearpolarization state, whereby a totally reflective state of operation anda semi-transparent state of operation are provided over theelectromagnetic region of the electromagnetic spectrum.

A further object of the present invention is to provide anelectro-optical glazing structure, comprising an electrically-activeπ-phase retardation panel interposed between a pair ofelectrically-passive electromagnetic radiation polarizing panels, bothof which are capable of reflecting electromagnetic radiation of a linearpolarization state, one is parallel to other, whereby a totallyreflective state of operation and a semi-transparent state of operationare provided over the electromagnetic region of the electromagneticspectrum.

A further object of the present invention is to provide anelectro-optical glazing structure, comprising an electrically-activeπ-phase retardation panel interposed between a pair ofelectrically-passive electromagnetic radiation polarizing panels, bothof which are capable of reflecting electromagnetic radiation of a linearpolarization state, one is perpendicular to other, whereby a totallyreflective state of operation and a semi-transparent state of operationare provided over the electromagnetic region of the electromagneticspectrum.

A further object of the present invention is to provide anelectro-optical glazing structure, comprising an electrically-activeπ-phase retardation panel interposed between a pair ofelectrically-passive cholesteric liquid crystal (CLC) electromagneticradiation polarizing panels, both of which are capable of reflectingelectromagnetic radiation of a LHCP state, whereby a totally reflectivestate of operation and a semi-transparent state of operation areprovided over the electromagnetic region of the electromagneticspectrum.

A further object of the present invention is to provide anelectro-optical glazing structure, comprising an electrically-activeπ-phase retardation panel interposed between a pair ofelectrically-passive CLC electromagnetic radiation polarizing panels,both of which are capable of reflecting electromagnetic radiation of aRHCP state, whereby a totally reflective state of operation and asemi-transparent state of operation are provided over a broad-bandregion of the electromagnetic spectrum.

A further object of the present invention is to provide anelectro-optical glazing structure, comprising an electrically-activeπ-phase retardation panel interposed between a pair ofelectrically-passive CLC electromagnetic radiation polarizing panels,one of which is capable of reflecting electromagnetic radiation of theLHCP state and the other of which is capable of reflectingelectromagnetic radiation of the RHCP state, whereby a totallyreflective state of operation and a semi-transparent state of operationare provided over a broad-band region of the electromagnetic spectrum.

A further object of the present invention is to provide anelectro-optical glazing structure, comprising an electrically-passiveπ-phase retardation panel interposed between a pair ofelectrically-active CLC electromagnetic radiation polarizing panels,both of which are capable of reflecting electromagnetic radiation of theLHCP state, whereby a totally reflective state of operation and atotally transparent state of operation are provided over a broad-bandregion of the electromagnetic spectrum.

A further object of the present invention is to provide anelectro-optical structure, comprising an electrically-passive π-phaseretardation panel interposed between a pair of electrically-active CLCelectromagnetic radiation polarizing panels, both of which are capableof reflecting electromagnetic radiation of the RHCP state, whereby atotally reflective state of operation and a semi-transparent state ofoperation are provided over a broad-band region of the electromagneticspectrum.

A further object of the present invention is to provide anelectro-optical glazing structure, comprising a pair ofelectrically-active CLC electromagnetic radiation polarizing panels, oneof which is capable of reflecting electromagnetic radiation of the LHCPstate and the other of which is capable of reflecting electromagneticradiation of the RHCP state, whereby a totally reflective state ofoperation and a totally transparent state of operation are provided overa broad-band region of the electromagnetic spectrum.

Another object of the present invention is to provide anactively-controlled window or viewing panel constructed from theelectro-optical glazing structure of the present invention, wherein thetransmission of electromagnetic radiation can be dynamically controlledover a broad-band region of the electromagnetic spectrum, between 50%transmission to 100% reflection and between 100% transmission to 100%reflection.

Another object of the present invention is to provide anactively-controlled window or viewing panel constructed from theelectro-optical glazing structure of the present invention, wherein thetransmission of electromagnetic radiation over the UV and IR regions ofthe electromagnetic spectrum can be totally reflected, rather thanabsorbed, reducing the temperature cycle range which the windowstructure is required to undergo.

Another object of the present invention is to combine theelectro-optical glazing panel of the present invention with acontrollable scattering layer or structure in order to scatter lighttransmitted therethrough or reflected therefrom.

Another object of the present invention is to provide anactively-controlled window or viewing panel constructed from theelectro-optical glazing structures of the present invention, whereinonly UV and IR radiation is reflected at the window surface, whileelectromagnetic radiation over the visible band is transmitted to theinterior environment being maintained under thermal control.

Another object of the present invention is to provide an intelligentwindow system for installation within a house or office building, oraboard a transportation vehicle such as an airplane or automobile,wherein the electro-optical glazing structure thereof is supportedwithin a prefabricated window frame, within which are mounted: aelectromagnetic-sensor for sensing electromagnetic conditions in theoutside environment; a battery supply for providing electrical power; aelectromagnetic-powered battery recharger for recharging the battery;electrical circuitry for producing glazing control voltages for drivingthe electrically-active elements of the electro-optical glazingsupported within the window frame; and a micro-computer chip forcontrolling the operation of the battery recharger and electricalcircuitry and the production of glazing control voltages as required bya radiation flow control program stored within the programmedmicrocontroller.

A further object of the present invention is to provide such anelectro-optical window structure which is designed for integrationwithin the heating/cooling system of a house, office building, factoryor vehicle in order to control the flow of broad-band electromagneticradiation through the electro-optical window structure, while minimizingthermal loading upon the heating/cooling system thereof.

Another object of the present invention is to provide a thermal/viewingshield or panel made from electro-optical glazing structure of thepresent invention.

Another object of the present invention is to provide of an intelligentpair of sunglasses, in which each optical element is realized using anelectro-optical glazing structure of the present invention, fashioned tothe dimensions of a sunglass frame.

Another object of the present invention is to provide of an intelligentpair of shutter glasses, in which each optical element is realized usingan electro-optical glazing structure of the present invention, fashionedto the dimensions of a shutter glass frame.

Another object of the present invention is to provide an intelligentwindshield or viewing screen, which is realized from an electro-opticalglazing structure of the present invention.

These and other objects of the present invention will become apparenthereinafter and in the Claims to Invention.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the Object of the PresentInvention, the following Detailed Description of the IllustrativeEmbodiments of the Present Invention should be read in conjunction withthe accompanying Drawings, wherein:

FIG. 1A is a perspective view of a generalized embodiment of theintelligent electro-optical window system of the present invention,wherein the electro-optical glazing structure thereof is electricallyswitched under microcomputer-control to its totally-reflecting state ofoperation upon detecting a first set of preprogrammed electromagneticconditions, whereby broad-band electromagnetic radiation is completelyreflected off the electro-optical glazing structure thereof;

FIG. 1B is a perspective view of the generalized embodiment of theintelligent electro-optical window system shown in FIG. 1A, wherein theelectro-optical glazing structure thereof is electrically switched undermicrocomputer-control to its transmission state of operation upondetecting a second set of preprogrammed electromagnetic conditions,where broad-band electromagnetic radiation is transmitted through theelectro-optical glazing structure thereof;

FIG. 2 is an exploded perspective view of a first illustrativeembodiment of the electro-optical glazing structure of the presentinvention, showing an electrically-active π-phase retardation panelinterposed between a pair of electrically-passive RHCP electromagneticradiation reflecting panels, each made from CLC material havingpolarization-selective reflection characteristics over a broad-bandregion of the electromagnetic spectrum;

FIG. 2A is a schematic diagram of the RHCP electromagnetic radiationreflecting panel shown in FIG. 2, and its response to both RHCP and LHCPelectromagnetic radiation incident thereto;

FIG. 2B is a schematic representation of the electromagnetic radiationreflection characteristics of the RHCP electromagnetic radiationreflecting panels of the glazing structure of FIG. 2, over its broadbandrange of operation, αλ_(reflection) ^(RHCP);

FIG. 2C is a schematic representation of a first embodiment of theπ-phase retardation panel used in the construction of the glazingstructure of FIG. 2, illustrating its operating characteristics inresponse to different glazing control voltages;

FIG. 2D is a schematic representation of a second embodiment of theπ-phase retardation panel used in the construction of the glazingstructure of FIG. 2, illustrating its operating characteristics inresponse to different glazing control voltages;

FIG. 2E1 is a schematic diagram of a super broad-band π-phaseretardation panel construction formed by interposing a twisted nematic,super-twisted nematic or cholesteric liquid crystal cell between a pairof electrically-passive broad-band π/2 phase retardation panels;

FIG. 2E2 is a schematic diagram of a broad-band π-phase retardationpanel employed in the electrically-switchable super-broad bandphase-retardation panel shown in FIG. 2E1, made by laminating aplurality of narrow-band or broad-band π/2 layers, each realized using amaterial having a different birefringence and its π/2 phase-retardationcharacteristics centered about a different wavelength;

FIG. 2E3 is a graphical representation of the resulting π/2 phaseretardation characteristics provided by the cooperation of the phaseretardatation characteristics of the individual narrow-band orbroad-band π/2 layers used to construct the electrically-passivesuper-broad band π/2 phase-retardation panel shown in FIG. 2E2;

FIG. 3A is a schematic diagram illustrating the operation of the glazingstructure of FIG. 2, wherein the π-phase retardation panel of FIG. 2C isused and the control voltage provided thereto is selected (i.e., V=0,φ=π) so that the window panel is switched into its optically opaque orreflection state of operation;

FIG. 3B is a schematic diagram illustrating the operation of theintelligent electro-optical window of FIG. 2, where the π-phaseretardation panel of FIG. 2C is used and the control voltage providedthereto is selected (i.e., V=1, 0) so that the window panel is switchedinto its the optically transparent (i.e. semi-clear) state of operation;

FIG. 4 is an exploded perspective view of a second illustrativeembodiment of the intelligent electro-optical window of the presentinvention, comprising an electrically-active π-phase retardation panelinterposed between a pair of electrically-passive LHCP electromagneticradiation reflecting panels, each made from CLC material havingpolarization-selective reflection characteristics over a broad-bandregion of the electromagnetic spectrum;

FIG. 4A is a schematic diagram of the LHCP electromagnetic radiationreflecting panel shown in FIG. 4, and its response to both RHCP and LHCPelectromagnetic radiation incident thereto;

FIG. 4B is a schematic representation of the electromagnetic radiationreflection characteristics of the LHCP electromagnetic radiationreflecting panels of the window of FIG. 4, over its broadband range ofoperation, αλ_(reflection) ^(LHCP);

FIG. 5A is a schematic diagram illustrating the operation of theintelligent electro-optical window of FIG. 4, where the π-phaseretardation panel of FIG. 2D is used and the control voltage providedthereto is selected (i.e., v=1, φ=π) so that the window panel isswitched into its the opaque or reflection state of operation;

FIG. 5B is a schematic diagram illustrating the operation of theintelligent electro-optical window of FIG. 5, where the π-phaseretardation panel of FIG. 5D is used and the control voltage providedthereto is selected (I.e., V=0, φ=0) so that the window panel isswitched into its optically semi-transparent (i.e., semi-clear) state ofoperation;

FIG. 6 is an exploded perspective view of a third illustrativeembodiment of the intelligent electro-optical window of the presentinvention, comprising an electrically-active π-phase retardation panelinterposed between an electrically-passive RHCP electromagneticradiation reflecting panel and an electrically-passive LHCPelectromagnetic radiation reflecting panel, each made from CLC materialhaving polarization-selective reflection characteristics over abroad-band region of the electromagnetic spectrum;

FIG. 6A is a schematic diagram of the LHCP electromagnetic radiationreflecting panel shown in FIG. 6, and its response to both RHCP and LHCPelectromagnetic radiation incident thereto;

FIG. 6B is a schematic representation of the electromagnetic radiationreflection characteristics of the LHCP electromagnetic radiationreflecting panel of the window of FIG. 6, over its broadband range ofoperation, αλ_(reflection) ^(RHCP);

FIG. 6C is a schematic diagram of the RHCP electromagnetic radiationreflecting panel shown in FIG. 6, and its response to both RHCP and LHCPelectromagnetic radiation incident thereto;

FIG. 6D is a schematic representation of the electromagnetic radiationreflection characteristics of the RHCP electromagnetic radiationreflecting panel of the window of FIG. 6, over its broadband range ofoperation, αλ_(reflection) ^(LHCP);

FIG. 7A is a schematic diagram illustrating the operation of theintelligent electro-optical window of FIG. 6, where the π-phaseretardation panel of FIG. 2C is used and the control voltage providedthereto is selected (i.e., v=0, φ=π) so that the window panel isswitched into its the optically semi-transparent (i.e. semi-clear) stateof operation;

FIG. 7B is a schematic diagram illustrating the operation of theintelligent electro-optical window of FIG. 6, where the π-phaseretardation panel of FIG. 2C is used and the control voltage providedthereto is selected (i.e., v=0, φ=0) so that the window panel isswitched into its optically opaque or reflection state of operation;

FIG. 8 is an exploded perspective view of a fourth illustrativeembodiment of the intelligent electro-optical window of the presentinvention, comprising an electrically-active polarization rotation panelinterposed between an electrically-passive linear polarizing (LP1)electromagnetic radiation reflecting panel and an electrically-passiveLP1 electromagnetic radiation reflecting panel, each made from CLCmaterial having polarization-selective reflection characteristics over abroad-band region of the electromagnetic spectrum;

FIG. 8A is a schematic diagram of the LP1 electromagnetic radiationreflecting panel shown in FIG. 8, and its response to both LP1 and LP2electromagnetic radiation incident thereto;

FIG. 8B is a schematic representation of the electromagnetic radiationreflection characteristics of the LP1 electromagnetic radiationreflecting panel of the window of FIG. 8, over its broadband range ofoperation, αλ_(reflection) ^(LP1);

FIG. 8C is a schematic diagram of the LP2 electromagnetic radiationreflecting panel shown in FIG. 8, and its response to both LP1 and LP2electromagnetic radiation incident thereto;

FIG. 8D is a schematic representation of the electromagnetic radiationreflection characteristics of the LP2 electromagnetic radiationreflecting panel of the window of FIG. 8, over its broadband range ofoperation, αλ_(reflection) ^(LP1);

FIG. 8E is a schematic representation of an illustrative embodiment ofthe electro-optical glazing structure of FIG. 8, in which anelectrically-switchable linear polarization direction rotating panel,realized using an electrically-controlled birefringence (ECB) cell,surface stablized ferroelectric liquid crystal (SSFLC) cell, twistednematic cell, super-twisted nematic cell, or cholesteric liquid crystalcell, is interposed between a pair of electrically-passive linearbroad-band polarizing reflective panels realized using (1) broad-bandCLC films with π/2 phase-retardation surfaces integrally formed thereinand/or other types of reflective linear polarizers such as multi-layerinterference linear polarizers;

FIG. 9A is a schematic diagram illustrating the operation of theintelligent electro-optical window of FIG. 8, where the linearpolarization direction rotating panel of FIG. 8 is used and the controlvoltage provided thereto is selected (i.e., v=0, 90 degrees rotation) sothat the window panel is switched into its transmission or semi-clearstate of operation;

FIG. 9B is a schematic diagram illustrating the operation of theintelligent electro-optical window of FIG. 9, where the linearpolarization direction rotating panel of FIG. 8 is used and the controlvoltage provided thereto is selected (i.e., v=1, zero degrees rotation)so that the window panel is switched into its optically opaque state ofoperation;

FIG. 10 is an exploded perspective view of a fifth illustrativeembodiment of the intelligent electro-optical window of the presentinvention, comprising an electrically-passive π-phase retardation panelinterposed between a first electrically-active LHCP electromagneticradiation reflecting panel and a second electrically active LHCPelectromagnetic radiation reflecting panel, each made from CLC materialhaving polarization-selective reflection characteristics over abroad-band region of the electromagnetic spectrum;

FIG. 10A is a schematic diagram of the LHCP electromagnetic radiationreflecting panel shown in FIG. 10, and its response to both RHCP andLHCP electromagnetic radiation incident thereto when operated in theLHCP radiation reflecting state thereof;

FIG. 10B is a schematic representation of the electromagnetic radiationreflection characteristics of the LHCP electromagnetic radiationreflecting panels of FIG. 10, over the broadband range of operationthereof αλ_(reflection) ^(LHCP), when operated in the LHCP radiationreflecting state thereof;

FIG. 10C is a schematic diagram of the LHCP electromagnetic radiationreflecting panel shown in FIG. 10, and its response to both RHCP andLHCP electromagnetic radiation incident thereto when operated in theradiation transmission state thereof;

FIG. 10D is a schematic representation of the electromagnetictransmission characteristics of the LHCP electromagnetic radiationreflecting panels of FIG. 10, over the broadband range of operationthereof αλ_(transmission) ^(LHCP), when operated in the radiationtransmission state thereof;

FIG. 10E is a schematic diagram illustrating the operation of theintelligent electro-optical window of FIG. 10, where the controlvoltages provided to both LHCP electromagnetic radiation reflectingpanels are selected so that the window panel is switched into its theoptically opaque state of operation;

FIG. 10F is a schematic diagram illustrating the operation of theintelligent electro-optical window of FIG. 10, where the controlvoltages provided to both LHCP electromagnetic radiation reflectingpanels are selected so that the window panel is switched into its theoptically transparent (i.e. clear) state of operation;

FIG. 11 is schematic cross-sectional diagram illustrating theconstruction of the first illustrative embodiment of theelectrically-switchable, circularly polarizing CLC panels used in theelectro-optical glazing structures of FIGS. 10, 12 and 14;

FIG. 11A1 is a graphical representation of the reflectioncharacteristics of the first embodiment of the electrically-switchablebroad-band CLC panel of FIG. 10, measured prior to UV polymerization ofthe CLC material contained within the ITO coated substrate plates of thepanel, using un-polarized light;

FIG. 11A2 is a graphical representation of the reflectioncharacteristics of the first embodiment of the electrically-switchablebroad-band CLC panel of FIG. 10, measured subsequent to UVpolymerization of the CLC material contained within the ITO coatedsubstrate plates of the panel, using right-handed and left-handedcircularly polarized light;

FIG. 11A3 is a graphical representation of the reflectioncharacteristics of the first embodiment of the electrically-switchablebroad-band CLC panel of FIG. 10, measured during electrically inactive(no voltage applied) and electrically-active (voltage applied) states ofoperation using right-handed circularly polarized light;

FIG. 12 is an exploded perspective view of a sixth illustrativeembodiment of the intelligent electro-optical window of the presentinvention, comprising an electrically-passive π-phase retardation panelinterposed between a first electrically-active RHCP electromagneticradiation reflecting panel and a second electrically-active RHCPelectromagnetic radiation reflecting panel, each made from CLC materialhaving polarization-selective reflection characteristics over abroad-band region of the electromagnetic spectrum;

FIG. 12A is a schematic diagram of the LHCP electromagnetic radiationreflecting panel shown in FIG. 12, and its response to both RHCP andLHCP electromagnetic radiation incident thereto when operated in theRHCP radiation reflecting state thereof;

FIG. 12B is a schematic representation of the electromagnetic radiationreflection characteristics of the RHCP electromagnetic radiationreflecting panels of FIG. 12, over the broadband range of operationthereof αλ_(reflection) ^(RHCP), when operated in the RHCP radiationreflecting state thereof;

FIG. 12C is a schematic diagram of the RHCP electromagnetic radiationreflecting panel shown in FIG. 12, and its response to both RHCP andLHCP electromagnetic radiation incident thereto when operated in theradiation transmission state thereof;

FIG. 12D is a schematic representation of the electromagnetictransmission characteristics of the RHCP electromagnetic radiationreflecting panels of FIG. 12, over the broadband range of operationthereof αλ_(transmission) ^(RHCP), when operated in the radiationtransmission state thereof;

FIG. 13A is a schematic diagram illustrating the operation of theintelligent electro-optical window of FIG. 12, where the controlvoltages provided to both RHCP electromagnetic radiation reflectingpanels are selected so that the window panel is switched into its theoptically opaque state of operation;

FIG. 13B is a schematic diagram illustrating the operation of theintelligent electro-optical window of FIG. 12, where the controlvoltages provided to both RHCP electromagnetic radiation reflectingpanels are selected so that the window panel is switched into its theoptically transparent (i.e. clear) state of operation;

FIG. 14 is an exploded perspective view of a seventh illustrativeembodiment of the intelligent electro-optical window of the presentinvention, showing an electrically-active LHCP electromagnetic radiationreflecting panel laminated to an electrically-active RHCPelectromagnetic radiation reflecting panel, each made from CLC materialhaving polarization-selective reflection characteristics over abroad-band region of the electromagnetic spectrum;

FIG. 14A is a schematic diagram of the LHCP electromagnetic radiationreflecting panel shown in FIG. 14, and its response to both RHCP andLHCP electromagnetic radiation incident thereto when operated in itsLHCP radiation reflecting state;

FIG. 14B is a schematic representation of the electromagnetic radiationreflection characteristics of the LHCP electromagnetic radiationreflecting panel of FIG. 14, over its broadband range of operationαλ_(reflection) ^(LHCP), when operated in its LHCP radiation reflectingstate;

FIG. 14C is a schematic diagram of the LHCP electromagnetic radiationreflecting panel shown in FIG. 14, and its response to both RHCP andLHCP electromagnetic radiation incident thereto when operated in itsradiation transmission state;

FIG. 14D is a schematic representation of the electromagnetic radiationtransmission characteristics of the LHCP electromagnetic radiationreflecting panel of FIG. 14, over its broadband range of operationαλ_(transmission) ^(LHCP), when operated in its radiation transmissionstate;

FIG. 14E is a schematic diagram of the RHCP electromagnetic radiationreflecting panel shown in FIG. 14, and its response to both RHCP andLHCP electromagnetic radiation incident thereto when operated in itsRHCP radiation reflecting state;

FIG. 14F is a schematic representation of the electromagnetic radiationreflection characteristics of the RHCP electromagnetic radiationreflecting panel of FIG. 14, over its broadband range of operationαλ_(reflection) ^(RHCP), when operated in its RHCP radiation reflectingstate;

FIG. 14G is a schematic diagram of the RHCP electromagnetic radiationreflecting panel shown in FIG. 14, and its response to both RHCP andLHCP electromagnetic radiation incident thereto when operated in itsradiation transmission state;

FIG. 14H is a schematic representation of the electromagnetic radiationtransmission characteristics of the RHCP electromagnetic radiationreflecting panel of FIG. 14, over its broadband range of operationαλ_(transmission) ^(RHCP), when operated in its radiation transmissionstate;

FIG. 15A is a schematic diagram illustrating the operation of theintelligent electro-optical window of FIG. 14, where the controlvoltages provided to both LHCP and RHCP electromagnetic radiationreflecting panels are selected so that the window panel is switched intoits the optically opaque state of operation;

FIG. 15B is a schematic diagram illustrating the operation of theintelligent electro-optical window of FIG. 14, where the controlvoltages provided to both RHCP electromagnetic radiation reflectingpanels are selected so that the window panel is switched into its theoptically transparent (i.e. clear) state of operation;

FIG. 16A is a schematic diagram of a second, alternative embodiment ofthe electrically-switchable broad-band CLC panel of FIG. 14, showing aportion of un-polarized light being polarized in a first polarizationstate and reflected off CLC microflakes (i.e. CLC pigments) that areoriented in a parallel manner within electrically-active host nematicliquid crystal molecules homogeneously aligned between a pair of ITOcoated plates, across which no control voltage is applied, while asecond portion of the un-polarized light is polarized in a secondpolarization state and transmitted through the oriented CLC microflakes;

FIG. 16B is a schematic diagram of the second embodiment of theelectrically-switchable broad-band CLC panel of FIG. 14, showing theun-polarized light being transmitted between CLC microflakes that areoriented in a vertical manner within electrically-active host nematicliquid crystal molecules homotropically aligned between a pair of ITOcoated plates, across which a control voltage is applied;

FIGS. 17A and 17B show a first illustrative embodiment of anelectrically-controllable light scattering structure mountable to anyembodiment of the electro-optical glazing structure of the inventiondisclosed or taught herein in order to scatter that portion of incidentlight which is not reflected during its reflection-mode of operation,thereby improving the privacy function of the glazing structure in thereflection mode;

FIGS. 18A and 18B show a second illustrative embodiment of anelectrically-controllable light scattering structure mountable to anyembodiment of the electro-optical glazing structure of the inventiondisclosed or taught herein in order to reflect that portion of incidentlight which is not reflected during its reflection-mode of operation,thereby improving the privacy function of the glazing structure in thereflection mode;

FIG. 18C shows a third illustrative embodiment of anelectrically-controllable light scattering structure mountable to anyembodiment of the electro-optical glazing structure of the inventiondisclosed or taught herein in order to scatter that portion of incidentlight which is not reflected during its reflection-mode of operation,thereby improving the privacy function of the glazing structure in thereflection mode;

FIG. 19 shows a fourth illustrative embodiment of anelectrically-controllable light scattering structure mountable to anyembodiment of the electro-optical glazing structure of the inventiondisclosed or taught herein in order to scatter that portion of incidentlight which is not reflected during its reflection-mode of operation,thereby improving the privacy function of the glazing structure in thereflection mode;

FIG. 19A shows the electro-optical light scattering structure of FIG. 19operated in its transmission mode, wherein no external voltage isapplied (i.e. V=V_(off));

FIGS. 19B and 19C show transmission and reflection characteristics forthe mode of operation indicated in FIG. 19A;

FIG. 19D shows the electro-optical light scattering structure of FIG. 19operated in its light scattering mode, wherein an external voltage V isapplied across the ITO surfaces (i.e. V=V_(on));

FIGS. 19E and 19F show transmission and reflection characteristics forthe mode of operation indicated in FIG. 19D;

FIG. 20 shows a fifth illustrative embodiment of anelectrically-controllable light scattering structure mountable to anyembodiment of the electro-optical glazing structure of the inventiondisclosed or taught herein in order to scatter that portion of incidentlight which is not reflected during its reflection-mode of operation,thereby improving the privacy function of the glazing structure in thereflection mode;

FIG. 20A shows the electro-optical light scattering structure of FIG. 20operated in its light scattering mode, wherein no external voltage isapplied (i.e. V=V_(off));

FIGS. 20B and 20C show transmission and reflection characteristics forthe mode of operation indicated in FIG. 20A;

FIG. 20D shows the electro-optical light scattering structure of FIG. 20operated in its light transmission mode, wherein an external voltage Vis applied across the ITO surfaces (i.e. V=V_(on));

FIGS. 20E and 20F show transmission and reflection characteristics forthe mode of operation indicated in FIG. 20D;

FIGS. 21 through 21F provide a generalized description of theillustrative embodiment disclosed in FIGS. 6 and 8, wherein theelectrically-passive broad-band polarizing layers have differenthandedness in both the circularly polarizing (RHCP/LHCP) and linearlypolarizing (LP1/LP2) system configurations;

FIGS. 22 through 22F provide a generalized description of theillustrative embodiments disclosed in FIGS. 2 and 4, wherein theelectrically-passive broad-band polarizing layers have the samehandedness in both the circularly polarizing (LHCP/LHCP or RHCP/RHCP)and linearly polarizing (LP1/LP1 or LP2/LP2) system configurations.

FIGS. 23 through 23F provide a generalized description of theillustrative embodiment disclosed in FIGS. 14 through 15B, wherein theelectrically-active broad-band polarizing layers have a differenthandedness in the circularly polarizing (LHCP/LHCP or RHCP/RHCP) systemconfigurations, and there is no optically active element disposedbetween the electrically-active polarizing layers;

FIG. 24 shows an illustrative embodiment of the electro-optical glazingstructure of the present invention comprising (1) a pair ofelectrically-passive broadband IR reflective polarizing panels forreflecting incident LHCP and RHCP light within the broad IR band andtransmitting all other components of light, and (2) anelectrically-controlled light scattering panel for selectivelyscattering light over the visible band (when no external voltage isapplied) so as to render the resulting glazing structure opaque toprovide privacy behind the window structure into which is installed;

FIG. 24A shows the electro-optical glazing structure of FIG. 24 operatedin scattering mode, wherein no external voltage (i.e. V=V_(off)) isapplied to the electrically-controlled scattering panel;

FIGS. 24B and 24C show transmission and reflection characteristics forthe mode of operation shown in FIG. 24A;

FIG. 24D shows the electro-optical light glazing structure of FIG. 24operated in its total-transmission mode, wherein an external voltage V(i.e. V=V_(on)) is applied to electrically-controlled light scatteringpanel;

FIGS. 24E and 24F show the transmission and reflection characteristicsfor the mode of operation shown in FIG. 24D;

FIG. 25 shows an other illustrative embodiment of the electro-opticalglazing structure of the present invention which is the reverse mode ofthe electro-optical glazing structure shown in FIG. 24;

FIG. 25A shows the electro-optical glazing structure of FIG. 25 operatedin its light transmission mode, wherein no external voltage (i.e.V=V_(off)) is applied to the electrically-controlled scattering panel;

FIGS. 25B and 25C show transmission and reflection characteristics forthe mode of operation shown in FIG. 25A;

FIG. 25D shows the electro-optical light glazing structure of FIG. 24operated in its light scattering mode, wherein an external voltage V(i.e. V=V_(on)) is applied to electrically-controlled light scatteringpanel;

FIGS. 25E and 25F show transmission and reflection characteristics forthe mode of operation shown in FIG. 25D;

FIG. 26 shows another embodiment of the electro-optical glazingstructure of the present invention constructed by adding the broad-bandIR filter panel shown in FIGS. 24 and 25, to the electro-optical glazingstructure shown in FIG. 22, wherein the broadband polarizing panels areeach of the same handedness (e.g. RHCP/RHCP or LP1/LP1);

FIG. 26A shows the electro-optical glazing structure of FIG. 26 operatedin its total-transmission mode, wherein no external voltage (i.e.V=V_(off)) is applied to the π phase shifting panel disposed between thepair of broadband polarizing reflective panels thereof;

FIGS. 26B and 26C show transmission and reflection characteristics forthe mode of operation shown in FIG. 26A;

FIG. 26D shows the electro-optical light glazing structure of FIG. 26operated in its partial-reflection/transmission mode, wherein anexternal voltage V (i.e. V=V_(on)) is applied to the π phase shiftingpanel disposed between the pair of broadband polarizing reflectivepanels thereof;

FIGS. 26E and 26F show the transmission and reflection characteristicsfor the mode of operation shown in FIG. 26D;

FIG. 27 shows another embodiment of the electro-optical glazingstructure of the present invention which operates in the “reverse” modeof the glazing structure of FIG. 26, and is constructed by adding thebroad-band IR filter panel shown in FIGS. 24 and 25, to theelectro-optical glazing structure shown in FIG. 21, wherein thebroadband polarizing panels are each of different handedness (e.g.RHCP/LHCP or LP1/LP2);

FIG. 27A shows the electro-optical glazing structure of FIG. 27 operatedin its partial-reflection/transmission mode, wherein no external voltage(i.e. V=V_(off)) is applied to the π phase shifting panel disposedbetween the pair of broadband polarizing reflective panels thereof;

FIGS. 27B and 27C show transmission and reflection characteristics forthe mode of operation shown in FIG. 27A;

FIG. 27D shows the electro-optical light glazing structure of FIG. 27operated in its total-reflection mode, wherein an external voltage V(i.e. V=V_(on)) is applied to the π phase shifting panel disposedbetween the pair of broadband polarizing reflective panels thereof;

FIGS. 27E and 27F show transmission and reflection characteristics forthe mode of operation shown in FIG. 27D;

FIG. 28 shows another embodiment of the electro-optical glazingstructure of the present invention constructed by adding the broad-bandIR filter panel shown in FIGS. 24 and 25, to the electro-optical glazingstructure shown in FIG. 23, wherein the electrically-active broadbandpolarizing panels thereof are each of different handedness (i.e.RHCP/LHCP);

FIG. 28A shows the electro-optical glazing structure of FIG. 28 operatedin its total-reflection mode, wherein no external voltage (i.e.V=V_(off)) is applied to the electrically-active circularly-polarizingreflective panels thereof;

FIGS. 28B and 28C show transmission and reflection characteristics forthe mode of operation shown in FIG. 28A;

FIG. 28D shows the electro-optical light glazing structure of FIG. 26operated in its total-transmission mode, wherein an external voltage V(i.e. V=V_(on)) is applied to the electrically-activecircularly-polarizing reflective panels thereof;

FIGS. 28E and 28F shows transmission and reflection characteristics forthe mode of operation shown in FIG. 28D;

FIGS. 29A through 29C show a broad-band reflector for use inconstructing broad-band circularly (and linearly) polarizing reflectivepanels employed in any one of embodiments of the electro-optical glazingpanel hereof.

DETAILED DESCRIPTION OF THE ILLUSTRATIVE EMBODIMENTS OF THE PRESENTINVENTION

Referring now to the accompanying Drawings, illustrative embodiments ofthe intelligent electro-optical window of the present invention will bedescribed in great detail. In each of the figures, like structures andelements shall be indicated by like reference numerals.

In FIGS. 1A and 1B, a generalized embodiment of the intelligentelectro-optical glazing structure (i.e. window structure) of the presentinvention is shown installed within an environment (e.g. building orvehicle) having an interior space or volume adjacent the windowstructure. Typically, the interior space or volume functions as a formof human habitat, although there may be applications in which this isnot the case. Preferably, the intelligent electro-optical windowstructure 1 cooperates with the heating/cooling system 2A of a house,office building, factory or vehicle indicated by reference numeral 2. Insuch preferred applications, the function of the electro-optical windowstructure will be to selectively control the flow of electromagneticradiation through its electro-optical glazing structure and into theinterior space, in order to minimize or reduce thermal loading upon theheating/cooling system of the environment.

As shown in FIGS. 1A and 1B, the electro-optical glazing structure 1comprises an electro-optical glazing panel 3 securely supported within aprefabricated window frame 4 which can be realized using virtually anysuitable material such as, for example, plastic, metal, rubber, wood orcomposite material. Within the window frame, a number of systemsubcomponents are securely mounted, namely: a electromagnetic-radiationsensor 5 for sensing electromagnetic conditions in the outsideenvironment; a rechargeable-type battery 6 for producing electricalpower within the window frame; a electromagnetic-powered batteryrecharger 7 for recharging the rechargeable battery 6; amicro-controller (e.g. RISC-type micro-computer chip with onboard ROM,EPROM and RAM) 8 for controlling the battery recharger and glazingcontrol signals as required by a radiation flow control program storedwithin the micro-computer chip; and electrical circuitry 9, response toglazing control signals, for producing control voltages that are appliedto the electrically-active elements of the electro-optical glazingstructure 3 to electrically switch the same from one optical state toanother optical state under microcontroller control.

As shown in FIG. 1, when a first set of preprogrammed electromagneticconditions (e.g. a first prespecified band of electromagnetic radiationhaving power above a first prespecified power threshold) is detected byelectromagnetic-radiation sensor, the electro-optical glazing structure3 is electrically switched to its totally-reflecting state of operationunder the control of preprogrammed microcontroller 8. In thistotally-reflecting state of operation, visible and electromagneticradiation is completely reflected off the glazing structure over a broadband of spectral wavelengths (e.g. 400 to 750 nanometers).

As shown in FIG. 1B, when a second set of preprogrammed electromagneticconditions (e.g. a second prespecified band of electromagnetic radiationhaving power above a second prespecified power threshold) is detected byelectromagnetic-radiation sensor, the electro-optical glazing structure3 is electrically switched to its transmission state of operation underthe control of preprogrammed microcontroller 8. In this transmissionstate, visible and electromagnetic radiation is transmitted through theelectro-optical glazing structure over a broad band of spectralwavelengths (e.g. 300 to 1000 nanometers).

While only two particular reflection/transmission states are illustratedin the above generalized embodiment, it is understood that virtually anyset of reflection/transmission characteristics can be realized by thewindow structure of the present invention. In each such alternativeembodiment, a particular set of conditions can be predefined to triggera change in the optical state of the electro-optical glazing structureof the present invention. Then microcontroller is programmed to switchthe optical state of the glazing structure upon detecting thecorresponding condition. In alternative embodiments, the environmentalcondition or conditions which cause a switching operation, need not berelated to electromagnetic radiation, but may be related to moisture,barometric pressure, temperature, or any other parameter prespecifiedwithin the programmed microcontroller 8.

While in theory there exists an infinite number of embodiments of theelectro-optical glazing structure of the present invention, sixdifferent embodiments of the electro-optical glazing structure will bedescribed in detail below in order to illustrate the inventive featuresthereof. Notably, each electro-optical glazing structure of the presentinvention is realized using CLC material having polarization-selectivereflection characteristics over a broad-band of operation (i.e.selectively reflecting and/or transmitting RHCP and LHCP wavelengthsover the IR, visible and UV portions of the electromagnetic spectrum).An excellent tutorial and overview on the polarization-reflectiveproperties of CLC materials and principles of polarization stateconversion (i.e. linear-to-circular, circular-to-linear,linear-to-linear, circular-to-circular, unpolarized-to-linear, andunpolarized-to-circular) can be found in applicant's U.S. Pat. No.5,221,982, incorporated herein by reference in its entirety.

By virtue of such ultra broad-band operating characteristics of theelectro-optical glazing material hereof, and the novel panelconfigurations disclosed herein, it is now possible to provide a levelof electromagnetic radiation control hitherto unattainable by prior artsmart window systems and methodologies.

First Illustrative Embodiment of the Electro-Optical Glazing Structureof the Present Invention

The first illustrative embodiment of the electro-optical glazingstructure hereof will be described with reference to FIGS. 2 through 3B.As shown in FIG. 2, the electro-optical glazing structure of the firstillustrative embodiment 10 comprises: an electrically-active π-phaseretardation panel 11 interposed between a pair of electrically-passiveright-hand circularly polarized (RHCP) electromagnetic radiationreflecting panels 12A and 12B, respectively, for imparting a π-phaseretardation to electromagnetic radiation transmitted therethrough inresponse to optical-state control voltages applied across theelectrically-active π-phase retardation panel 11; and electricallyconductive means 13 for applying optical-state control voltages to theelectrically-active π-phase retardation panel 11. Preferably, theelectro-optical glazing structure of FIG. 2 is mounted within a framestructure as described in connection with the generalized embodimentshown in FIGS. 1A and 1B, and incorporates all of the power generation,electromagnetic radiation detection and micro-control mechanismsthereof.

As illustrated in FIGS. 2A and 2B, electromagnetic radiation having aRHCP polarization state and a wavelength inside the characteristicreflection bandwidth αλ_(reflection) ^(RHCP) of the RHCP electromagneticradiation reflecting panels 12A (12B) is 100% reflected directlytherefrom without absorption, while electromagnetic radiation havingeither a LHCP polarization state and/or a wavelength outside thecharacteristic reflection bandwidth αλ_(reflection) ^(RHCP) of the RHCPelectromagnetic radiation reflecting panels 12A (12B) is transmitted100% directly therethrough without absorption. Suchelectrically-passive, broad-band RHCP electromagnetic radiationreflecting panels can be made using the fabrication methods disclosed inInternationaL Publication No. WO 97/16762 entitled “Super Broad-BandPolarizing Reflective Material” incorporated herein by reference in itsentirety. Alternatively, narrow-band RHCP electromagnetic radiationreflecting panels 12A (12B) can be made using the fabrication methodsdisclosed in U.S. Pat. No. 5,221,982 to Faris, or using the techniquesdisclosed in U.S. Pat. No. 5,506,704 to Broer, et al. each beingincorporated herein by reference in its entirety.

There are a number of different ways in which to fabricate broad-bandelectromagnetic radiation reflecting panels 12A (12B) using the superbroad-band, broad-band, narrow-band and spectrally-tunable CLC filmstaught in the above-cited references.

For example, broad-band circularly polarizing reflective panels 12A(12B) can be fabricated by producing sheets of such CLC film and thenlaminating the CLC film sheets onto a surface of glass or like substratematerial physically associated with the electrically-switchableπ-retardation panel 11 interposed between the circularly polarizing CLCpanels, as shown in FIGS. 2, 4, and 6, in particular. Notably, using thespectral-tuning techniques disclosed in detail in InternationalPublication No. WO 97/16762, the CLC film hereof can be fabricated tohave virtually any desired set of polarization reflectioncharacteristics that would required by any particular application over asuper broad-band of operation (e.g. from the UV region to the IR regionof the electromagnetic spectrum).

Alternatively, sheets of super-broad-band, broad-band, narrow-bandand/or spectrally-tuned CLC film can be produced as taught in the abovereferences, and thereafter fragmented into microscopic sized CLCmicroflakes using film fragmentation techniques taught in U.S. Pat. No.5,364,557. Then the CLC microflakes can be added to an opticallytransparent carrier fluid to produce a CLC ink or paint that can then beapplied to the exterior surfaces of the glass substrates used toconstruct the electrically-switchable π retardation panel component ofelectro-optical glazing structures, of the type shown in FIGS. 2, 4 and6, for example. The concentration of the CLC microflakes and theviscosity of the carrier medium (e.g. lacquer, polymer, etc.) should beselected to ensure that when the coating of the CLC ink or paint isapplied to a substrate, the CLC microflakes will be distributed withinthe carrier medium so that incident light reflects from the resultingCLC coating in a non-specular manner. This will ensure that theresulting coating produces a “super-white” appearance in the eyes ofon-viewers, providing a high measure of privacy, as well as aestethicvalue, highly desired in window applications.

In the illustrative embodiment of the glazing structure of FIG. 2, thecharacteristic reflection bandwidth αλ_(reflection) ^(RHCP) of the RHCPelectromagnetic radiation reflecting panel 12A is designed to besubstantially the same as characteristic reflection bandwidthαλ_(reflection) ^(LHCP) of the LHCP electromagnetic radiation reflectingpanel 12B. It is understood, however, that in alternative embodiments ofthe present invention, such reflection bandwidth characteristics may bespecifically designed to partially overlap, or be separated from eachother on the wavelength (i.e. frequency) domain in to provide desiredreflection/transmission performance characteristics.

In general, a π-cell (i.e. π-retardation panel) or anelectrically-controlled birefrigence (ECB) panel can be used to realizethe electrically-switchable π-phase retardatation panel 11 employed inthe circularly polarizing reflective glazing structures of FIGS. 2, 4and 6 hereof. Preferably, the techniques disclosed in U.S. Pat. No.4,566,758 to Bos, incorporated herein by reference, are used tofabricate such electrically-switchable π-phase retardatation panels 11.For most applications, the bandwidth of prior art π-cells should besufficient to provide glazing structures having operatingcharacteristics over the visible portion of the electromagneticspectrum. However, in some instances, it will be desirable to provideelectro-optical glazing structures having super broad-band operation(i.e. from the IR region into the UV region of the spectrum). In suchapplications, it will be necessary to extend the π-phase retardatationcharacteristics of the electrically-switchable π-phase retardatationpanel beyond the visible band. The following technique may be used toconstruct electrically-active (switchable) π-retardation panels capableof super broad-band operation.

As shown in FIG. 2E1, an electrically-switchable super broadbandπ-retardation panel can be constructed by interposing anelectrically-active structure linear polarization direction rotatingpanel such as TN, or STN, or CLC cell, between a pair ofelectrically-passive super broad-band π/2 retardation panels (shifters).As shown in FIG. 2E2, each super broad-band π/2-retardation panel ismade by laminating, or depositing two or more broad-band or narrow-bandπ/2 retardation layers, each made from different material and having π/2phase retardation characteristics centered about at differentwavelength, as schematically shown in FIG. 2E3. These subcomponentbroad-band or narrow-band π/2 retardation layers can be made from liquidcrystal material, birefringent polymer, and crystals.

The function of each electrically-passive super-broad-band π/2retardation panel is to convert circularly polarized light into linearlypolarized light which can be polarization direction rotated by theelectrically switchable TN, or STN, or CLC cell sandwiched between thepair of super broad-band π/2 retardation layers. The function of the TN(twist nematic), or STN (super twist nematic), or CLC cell is to operateas an electrically-switchable optical rotator which rotates a linearpolarization light by 90° when there is no electric field is appliedacross its ITO surfaces. If an electric field is applied, the opticalrotation power of the elements disappears. This control over theelectric field allows the glazing structure to be switched from itstotal reflection state to its half reflection state, or vice versa. Whenthe electrically-switchable polarization direction rotator is made fromlow-molecular weight (LMW) liquid crystal material having a chiral phasewhen no voltage is applied, then its selective wavelength of the shouldbe located outside the window operating spectrum region. By controllingthe helix of the CLC molecules in the chiral phase, as well as the totalthickness thereof, a 90° rotation of a linear polarization can beachieved.

In general, there are two different ways to configureelectrically-switchable π retardation panel 11 in terms of externalcontrol voltages. In FIGS. 2C and 2D, these configurations arespecified.

In FIG. 2C, the first embodiment of the π-phase retardation panel 11 isshown along with a specification of its various states of operation. Asshown, when a non-zero voltage (e.g. 20 Volts) is applied across thephase retardation panel, 0-phase retardation is imparted toelectromagnetic radiation transmitted therethrough. When a controlvoltage of zero volts is applied across the phase retardation panel, itimparts a π-phase retardation to electromagnetic radiation transmittedtherethrough having a wavelength within its operating band αλ_(π) whichis typically 300-1000 nanometers.

In FIG. 2D, a second embodiment of the π-phase retardation panel isshown along with a specification of its states of operation. As shown,when a control voltage of zero volts is applied across this retardationpanel, it imparts a O-phase shift to electromagnetic radiation having awavelength within its operating band which is typically 350 nanometers,whereas π-phase retardation is imparted to such electromagneticradiation when a non-zero voltage (e.g. 5-50 Volts) is appliedthereacross. For wavelengths outside of the operating band, a phaseshift other than π-radians is imparted to incident electromagneticradiation when a non-zero voltage is applied.

Physically interfacing the subcomponent panels of the electro-opticalglazing structure of FIG. 2 can be achieved using conventionallamination techniques well known in the glazing art.

The operation of the glazing structure of FIG. 2 will now be describedwith reference to FIGS. 3A and 3B, where the π-phase retardation panelof FIG. 2C is used in the construction of the glazing structure.

As shown in FIG. 3A, the electro-optical glazing structure of FIG. 2 isswitched to its optically opaque state of operation by applying theappropriate control voltage thereacross (e.g. V=0 Volts). In thisoptical state, the electro-optical glazing structure reflects both LHCPand RHCP electromagnetic radiation within αλ_(reflection) ^(RHCP)incident the window panel independent of the direction of propagation.As such, the operation of this particular electro-optical glazingstructure is “symmetrical”. The physical mechanisms associated with suchreflection processes are schematically illustrated in FIG. 3A. Inasmuchas 100% of incident electromagnetic radiation is reflected from thesurface of the electro-optical glazing structure, this glazing structureis “totally reflective” in this state of operation.

As shown in FIG. 3B, the electro-optical glazing structure of FIG. 2 isswitched to its optically semi-transparent (i.e. semi-clear state) ofoperation by applying the appropriate control voltage thereacross (e.g.V=20 Volts). In this optical state, the electro-optical glazingstructure reflects RHCP electromagnetic radiation within αλ_(reflection)^(RHCP) incident the window panel independent of the direction ofpropagation, while transmitting LHCP electromagnetic radiation fallingincident the window panel independent of the direction ofelectromagnetic radiation propagation. The physical mechanismsassociated with such reflection and transmission processes areschematically illustrated in FIG. 3A. Inasmuch as 50% of incidentelectromagnetic radiation is transmitted through the electro-opticalglazing structure, while 50% of such electromagnetic radiation isreflected therefrom, this glazing structure can be said to “partiallytransmissive” in this state of operation.

Second Illustrative Embodiment of the Electro-Optical Glazing Structureof the Present Invention

The second illustrative embodiment of the electro-optical glazingstructure hereof will be described with reference to FIGS. 4 through 5B.As shown in FIG. 4, the electro-optical glazing structure of the secondillustrative embodiment 14 comprises: an electrically-active (i.e.switchable) π-phase retardation panel 11 interposed between a pair ofelectrically-passive left-hand circularly polarizing (LHCP)electromagnetic radiation reflecting panels 15A and 15B, respectively;and electrically conductive means 16 for applying optical-state controlvoltages to the electrically-active π-phase retardation panel 11.Preferably, the electro-optical glazing structure of FIG. 4 is mountedwithin a frame structure as described in connection with the generalizedembodiment shown in FIGS. 1A and 1B, and incorporates all of the powergeneration, electromagnetic radiation detection and micro-controlmechanisms thereof.

As illustrated in FIGS. 4A and 4B, electromagnetic radiation having aLHCP polarization state and a wavelength inside the characteristicreflection bandwidth αλ_(reflection) ^(LHCP) of the LHCP electromagneticradiation reflecting panels 15A, 15B is reflected directly therefromwithout absorption, while electromagnetic radiation having either a RHCPpolarization state and/or a wavelength outside the characteristicreflection bandwidth αλ_(reflection) ^(RHCP) of the LHCP electromagneticradiation reflecting panels is transmitted directly therethrough withoutabsorption. Such electrically-passive, broad-band LHCP electromagneticradiation reflecting panels can be made using the fabrication methodsdisclosed in International Publication No. WO 97/16762, supra. In thepreferred embodiment, the broad-band RHCP electromagnetic radiationreflecting panels 12A (12B) are fabricating by applying a coating ofCLC-based ink (with suspended CLC flakes therein) onto a conventionalglass panel, as taught in International Publication No. WO 97/16762,supra. Alternatively, narrow-band RHCP electromagnetic radiationreflecting panels can be made using the fabrication methods disclosed inU.S. Pat. No. 5,506,704 to Broer, et al, or the methods disclosed inU.S. Pat. No. 5,221,982 to Faris.

Physically interfacing panels 11, 15A and 15B of the electro-opticalglazing structure of FIG. 4 can be achieved using conventionallamination techniques well known in the glazing art.

In the illustrative embodiment of the glazing structure of FIG. 4,characteristic reflection bandwidth αλ_(reflection) ^(LHCP) of the LHCPelectromagnetic radiation reflecting panel 15A is designed to besubstantially the same as characteristic reflection bandwidthαλ_(reflection) ^(LHCP) of the LHCP electromagnetic radiation reflectingpanel 15B. It is understood, however, that in alternative embodiments ofthe present invention, such reflection characteristics may bespecifically designed to partially overlap, or be separated from eachother on the wavelength (i.e. frequency) domain in to provide desiredreflection/transmission performance characteristics.

The electrically-active π-retardation panel 11 can be constructed usingany of the techniques described in detail above.

The operation of the glazing structure of FIG. 4 will now be describedwith reference to FIGS. 5A and 5B, where the π-phase retardation panel11 of FIG. 2C is used in the construction of the glazing structure.

As shown in FIG. 5A, the electro-optical glazing structure of FIG. 4 isswitched to its optically opaque state of operation by applying theappropriate control voltage thereacross (i.e. V=0 Volts). In thisoptical state, the electro-optical glazing structure 14 reflects bothLHCP and RHCP electromagnetic radiation within αλ_(reflection) ^(LHCP)incident the window panel, independent of its direction of propagation.As such, the operation of this particular electro-optical glazingstructure is “symmetrical”. The physical mechanisms associated with suchreflection processes are schematically illustrated in FIG. 5A. Inasmuchas 100% of incident electromagnetic radiation is reflected from thesurface of the electro-optical glazing structure, this glazing structureis “totally reflective” in this state of operation.

As shown in FIG. 5B, the electro-optical glazing structure of FIG. 4 isswitched to its optically semi-transparent (i.e. semi-clear state) ofoperation by applying the appropriate control voltage thereacross (i.e.V=20 Volts). In this optical state, the electro-optical glazingstructure 14 reflects LHCP electromagnetic radiation withinαλ_(reflection) ^(LHCP) incident the window panel, independent of itsdirection of propagation, while transmitting RHCP electromagneticradiation within αλ_(reflection) ^(LHCP) incident the window panel,independent of the direction of electromagnetic radiation propagation.As such, the operation of this particular electro-optical glazingstructure is “symmetrical”. The physical mechanisms associated with suchreflection and transmission processes are schematically illustrated inFIG. 5A. Inasmuch as 50% of incident electromagnetic radiation istransmitted through the electro-optical glazing structure, while 50% ofsuch electromagnetic radiation is reflected therefrom, this glazingstructure is “partially transmissive” in this state of operation.

Third Illustrative Embodiment of the Electro-Optical Glazing Structureof the Present Invention

The third illustrative embodiment of the electro-optical glazingstructure hereof will be described with reference to FIGS. 6 through 7B.As shown in FIG. 6, the electro-optical glazing structure of the thirdillustrative embodiment 17 comprises: an electrically-active π-phaseretardation panel 11 interposed between an electrically-passive LHCPelectromagnetic radiation reflecting panel 18A and anelectrically-passive RHCP electromagnetic radiation reflecting panel18B; and electrically conductive means 19 for applying optical-statecontrol voltages to the electrically-active π-phase retardation panel11. Preferably, the electro-optical glazing structure of FIG. 6 ismounted within a frame structure as described in connection with thegeneralized embodiment shown in FIGS. 1A and 1B, and incorporates all ofthe power generation, electromagnetic radiation detection andmicro-control mechanisms thereof.

As illustrated in FIGS. 6A and 6B, electromagnetic radiation having aLHCP polarization state and a wavelength inside the characteristicreflection bandwidth αλ_(reflection) ^(LHCP) of the LHCP electromagneticradiation reflecting panel 18A is reflected directly therefrom withoutabsorption, while electromagnetic radiation having either a RHCPpolarization state and/or a wavelength outside the characteristicreflection band αλ_(reflection) ^(LHCP) of the LHCP electromagneticradiation reflecting panel is transmitted directly therethrough withoutabsorption. In the preferred embodiment, the broad-band RHCPelectromagnetic radiation reflecting panels 18A are fabricating byapplying a coating of CLC-based ink (with suspended CLC flakes therein)onto a conventional glass panel, as taught in International PublicationNo. WO 97/16762, and described hereinabove. Alternatively, narrow-bandRHCP electromagnetic radiation reflecting panels 18A can be made usingthe fabrication methods disclosed in U.S. Pat. No. 5,221,982 to Faris,and while less preferred, using the methods disclosed in U.S. Pat. No.5,506,704 to Broer, et al.

As illustrated in FIGS. 6C and 6D, electromagnetic radiation having aRHCP polarization state and a wavelength inside the characteristicreflection bandwidth αλ_(reflection) ^(RHCP) of the RHCP electromagneticradiation reflecting panel 18B is reflected directly therefrom withoutabsorption, while electromagnetic radiation having either a LHCPpolarization state and/or a wavelength outside the characteristicreflection bandwidth αλ_(reflection) ^(RHCP) of the RHCP electromagneticradiation reflecting panel is transmitted directly therethrough withoutabsorption. In the preferred embodiment, the broad-band RHCPelectromagnetic radiation reflecting panels 18B are fabricating byapplying a coating of CLC-based ink (with suspended CLC flakes therein)onto a conventional glass panel, as taught in International PublicationNo. WO 97/16762, and described hereinabove. Alternatively, narrow-bandRHCP electromagnetic radiation reflecting panels 18B can be made usingthe fabrication methods disclosed in U.S. Pat. No. 5,221,982 to Faris,and using the less preferred techniques disclosed in U.S. Pat. No.5,506,704 to Broer, et al.

In the illustrative embodiment of the glazing structure of FIG. 6,characteristic reflection bandwidth αλ_(reflection) ^(RHCP) of the RHCPelectromagnetic radiation reflecting panel 18B is designed to besubstantially the same as characteristic reflection bandwidthαλ_(reflection) ^(LHCP) of the LHCP electromagnetic radiation reflectingpanel 18A. It is understood, however, that in alternative embodiments ofthe present invention, such reflection bandwidth characteristics may bespecifically designed to partially overlap, or be separated from eachother on the wavelength (i.e. frequency) domain in to provide desiredreflection/transmission performance characteristics.

Electrically-active π retardation panel 11 can be realized using any ofthe construction techniques described in detail above. Physicallyinterfacing panels 11, 18A and 18B of the electro-optical glazingstructure of FIG. 6 can be achieved using conventional laminationtechniques well known in the glazing art.

The operation of the glazing structure of FIG. 6 will now be describedwith reference to FIGS. 7A and 7B, where the π-phase retardation panel11 of FIG. 2C is used in the construction of the glazing structure.

As shown in FIG. 7A, the electro-optical glazing structure of FIG. 6 isswitched to its semi-optically transparent (i.e. clear) state ofoperation by applying the appropriate control voltage thereacross (i.e.V=0 Volts). In this optical state, the electro-optical glazing structurereflects LHCP electromagnetic radiation within αλ_(reflection) ^(LHCP)incident on the LHCP electromagnetic radiation reflecting panel 18A ofthe window panel, while transmitting RHCP electromagnetic radiationwithin αλ_(reflection) ^(LHCP) incident thereto and converting the sameinto LHCP electromagnetic radiation by the π-phase shifter as itemanates from the RHCP electromagnetic radiation reflecting panel 18B.In this optical state, the electro-optical glazing structure reflectsRHCP electromagnetic radiation within αλ_(reflection) ^(RHCP) incidenton the RHCP electromagnetic radiation reflecting panel 18B of the windowpanel, while transmitting LHCP electromagnetic radiation withinαλ_(reflection) ^(RHCP) incident thereto and converting the same intoRHCP electromagnetic radiation as it emanates from the LHCPelectromagnetic radiation reflecting panel 18A. As such, the operationof this particular electro-optical glazing structure is “assymmetrical”.The physical mechanisms associated with such reflection andtransmission-reflection processes are schematically illustrated in FIG.7A in great detail. Inasmuch as 50% of incident electromagneticradiation is transmitted through the electro-optical glazing structure,while 50% of such electromagnetic radiation is reflected therefrom, thisglazing structure is “partially transmissive” in this state ofoperation.

As shown in FIG. 7B, the electro-optical glazing structure of FIG. 6 isswitched to its optically opaque state of operation by applying theappropriate control voltage thereacross (i.e. V=20 Volts). In thisoptical state, the electro-optical glazing structure reflects LHCP andRHCP electromagnetic radiation within αλ_(reflection) ^(LHCP) incidenton the LHCP electromagnetic radiation reflecting panel of the windowpanel. In this optical state, the electro-optical glazing structure 17also reflects RHCP and LHCP electromagnetic radiation withinαλ_(reflection) ^(RHCP) incident on the RHCP electromagnetic radiationreflecting panel 18B of the window panel. As such, the operation of thisparticular electro-optical glazing structure is “symmetrical”. Thephysical mechanisms associated with such reflection andtransmission-reflection processes are schematically illustrated in FIG.7B in great detail. Inasmuch as 100% of incident electromagneticradiation is reflected from the surface of the electro-optical glazingstructure, this glazing structure is “totally reflective” in this stateof operation.

Fourth Illustrative Embodiment of the Electro-Optical Glazing Structureof the Present Invention

The fourth illustrative embodiment of the electro-optical glazingstructure hereof will be described with reference to FIGS. 8 through 9B.As shown in FIG. 8, the electro-optical glazing structure of the fourthillustrative embodiment 19 comprises: an electrically-passive linearpolarization direction rotating panel 19C interposed between a firstelectrically-active linearly polarizing electromagnetic radiationreflecting panel 19A having linearly polarization state LP1, and asecond electrically-active LHCP electromagnetic radiation reflectingpanel 19C having linearly polarization state LP2, orthogonal to LP1 orparallel; and electrically conductive means 19D for applyingoptical-state control voltages to the electrically-active LHCPelectromagnetic radiation reflecting panels 19B and 19C. Preferably, theelectro-optical glazing structure of FIG. 8 is mounted within a framestructure as described in connection with the generalized embodimentshown in FIGS. 1A and 1B, and incorporates all of the power generation,electromagnetic radiation detection and micro-control mechanismsthereof.

In FIGS. 8A and 8B, the reflection characteristics ofelectrically-passive LP1 electromagnetic radiation reflecting panel 19Bare illustrated. As shown, electromagnetic radiation having a LP1polarization state and a wavelength inside the characteristic reflectionbandwidth αλ_(reflection) ^(LP1) of the LP1 electromagnetic radiationreflecting panel is reflected directly therefrom without absorption,while electromagnetic radiation having either a LP2 polarization stateand/or a wavelength outside the characteristic reflection bandwidthαλ_(reflection) ^(LP2) of the LP2 electromagnetic radiation reflectingpanel is transmitted directly therethrough without absorption.

In FIGS. 8C and 8D, the reflection characteristics ofelectrically-active LP2 electromagnetic radiation reflecting panel 19Care illustrated. As shown in FIGS. 8C and 8D, electromagnetic radiationhaving a LP1 polarization state and any wavelength within transmissionbandwidth αλ_(transmission) ^(LP2) is transmitted directly through theglazing panel without absorption, while electromagnetic radiation havingeither a LP2 polarization state and/or a wavelength outside thecharacteristic reflection bandwidth αλ_(reflection) ^(LP2) of the LP2electromagnetic radiation reflecting panel is transmitted directlytherethrough without absorption.

Electrically-passive LP1 and LP2 polarization reflective panels 19A and19B can be made from super broad-band CLC film taught in InternationalPublication No. WO 97/16762 by Reveo, Inc., and while less preferred,using the fabrication methods disclosed in U.S. Pat. No. 5,221,982 toFaris, and in U.S. Pat. No. 5,506,704 to Broer, et al, each of thesereferences incorporated herein by reference in its entirety. Theseapplications disclose how to make circularly polarizing reflective CLCfilms. Such films can be converted into linearly polarizing CLC filmsusing the novel phase-retardation imparting techniques taught in greatdetail in International application Ser. No. PCT/US97/20091 entitled“Liquid Crystal Film Structures With Phase-Retardation Surface RegionsFormed Therein” by Reveo, Inc., incorporated herein by reference in itsentirety. The methods taught therein allows one to make anelectrically-passive, broad-band linear polaring panel from a singlelayer of CLC film material, without laminating a π/2 phase-retardationpanel to a layer of circularly polarizing CLC film.

An alternative method of making broad-band linearly polarizingreflective panels 19A and 19B is disclosed in U.S. Pat. No. 5,506,704 toBroer, et al. However, the fabrication techniques disclosed therein areless preferred than those taught in International Application Serial No.PCT/US97/20091, as the technique disclosed in U.S. Pat. No. 5,506,704requires laminating a π/2 phase retardation panel to a circularlypolarizing CLC film layer, which complicates manufacture and increasesmanufacturing costs.

The electronically-switchable linear polarization direction rotatingpanel 19C employed in the electro-optical glazing structure of FIG. 8can be realized as an electrically-controlled birefrigence (ECB) cell,surface stabilized ferroelectric liquid crystal (SSFLC) cell, twistednematic (TN) liquid crystal cell, super-twisted nematic (STN) liquidcrystal cell, or CLC cell, whose operation is controlled by a controlvoltage well known in the art. To construct the linear polarizationrotating cell 19C, a layer of liquid crystal material is containedbetween a spaced apart pair of glass panels bearing layers of ITO on theinterior surfaces thereof, and rubbed polyimide to provide liquidcrystal alignment in a manner well known in the art. The ITO layers areused to create the necessary voltage across the layer of liquid crystalmaterial and align the liquid crystal molecules, thereby preventingrotation of the polarization direction of linearly polarized light beingtransmitted therethrough during operation of the electro-optical glazingstructure.

Physically interfacing panels 19A, 19B and 19C of the electro-opticalglazing structure of FIG. 8 can be achieved using conventionallamination techniques well known in the glazing art.

The operation of the glazing structure of FIG. 8 will now be describedwith reference to FIGS. 9A and 9B.

As shown in FIG. 9A, the electro-optical glazing structure of FIG. 8 isswitched to its optically opaque state of operation by not applying acontrol voltage thereacross (i.e. V=0). In this optical state, theelectro-optical glazing structure 19 reflects LP1 electromagneticradiation within αλ_(reflection) ^(LP1) incident on the LP1electromagnetic radiation reflecting panel without adsorption, whiletransmitting LP2 electromagnetic radiation within αλ_(reflection) ^(LP1)incident thereto without adsorption. Also in this optical state, theelectro-optical glazing structure 19 reflects LP2 electromagneticradiation within αλ_(reflection) ^(LP2) incident on the LP2electromagnetic radiation reflecting panel without adsorption, whiletransmitting LP1 electromagnetic radiation within αλ_(reflection) ^(LP2)incident thereto without adsorption. As such, the operation of thisparticular electro-optical glazing structure is “assymmetrical”. Thephysical mechanisms associated with such reflection processes areschematically illustrated in FIG. 9A in great detail. Inasmuch as 50% ofincident electromagnetic radiation is reflected from the electro-opticalglazing structure and 50% of incident electromagnetic radiation istransmitted through the electro-optical glazing structure, this glazingstructure is “partially reflective” in this state of operation.

As shown in FIG. 9B, the electro-optical glazing structure of FIG. 8 isswitched to its optically transparent (i.e. clear) state of operation byapplying the appropriate control voltage thereacross (i.e. V=1). In thisoptical state, the electro-optical glazing structure 19 reflects bothLP1 and LP2 electromagnetic radiation within αλ_(reflection) ^(LP1) andαλ_(reflection) ^(LP2) incident on either electromagnetic radiationreflecting panel of the window panel without adsorption, independent ofthe direction of propagation of the incident electromagnetic radiation.As such, the operation of this particular electro-optical glazingstructure is “symmetrical”. The physical mechanisms associated with suchtransmission processes are schematically illustrated in FIG. 9B in greatdetail. Inasmuch as 100% of incident electromagnetic radiation istransmitted through the electro-optical glazing structure, this glazingstructure is “totally opaque” in this state of operation.

The electro-optical glazing structure of FIG. 8 can be readily adaptedto exhibit “asymmetrical” reflection/transmission characteristics overits broad-band of operation by tuning the spectral transmissioncharacteristics of both the CLC-based LP1 and LP2 electromagneticradiation reflecting panels 19A and 19B of the illustrative embodimentso that the spectral reflection (and transmission) bandwidthcharacteristics thereof are either completely or partially overlappingor are separated on the wavelength (i.e. frequency) domain. Using suchCLC-tuning techniques, it is possible to create an electro-opticalglazing structure having the construction of FIG. 8 which, when switchedto its first optical state, is capable of totally reflectingelectromagnetic radiation within a desired reflection band (e.g. withinthe ultraviolet and infrared bands) in a first direction defined withrespect to the panel, and when switched to its second optical state,totally transmitting electromagnetic radiation within such reflectionband.

Fifth Illustrative Embodiment of the Electro-Optical Glazing Structureof the Present Invention

The fifth illustrative embodiment of the electro-optical glazingstructure hereof will be described with reference to FIGS. 10 through11C2.

As shown in FIG. 10, the electro-optical glazing structure of the fifthillustrative embodiment 20 comprises: an electrically-passive π-phaseretardation panel 21 interposed between a first electrically-active LHCPelectromagnetic radiation reflecting panel 22A and a secondelectrically-active LHCP electromagnetic radiation reflecting panel 22B;and electrically conductive means 23 for applying optical-state controlvoltages to the electrically-active LHCP electromagnetic radiationreflecting panels 22A and 22B. Preferably, the electro-optical glazingstructure of FIG. 10 is mounted within a frame structure as described inconnection with the generalized embodiment shown in FIGS. 1A and 1B, andincorporates all of the power generation, electromagnetic radiationdetection and micro-control mechanisms thereof.

In FIG. 10A, electrically-active LHCP electromagnetic radiationreflecting panel 22A is shown operated in its electrically inactivestate (i.e. when V=0). As shown in FIG. 10C, electromagnetic radiationhaving a LHCP polarization state and a wavelength inside thecharacteristic reflection bandwidth αλ_(reflection) ^(LHCP) of the LHCPelectromagnetic radiation reflecting panel is reflected directlytherefrom without absorption, while electromagnetic radiation havingeither a RHCP polarization state and/or a wavelength outside thecharacteristic reflection bandwidth αλ_(reflection) ^(LHCP) of the LHCPelectromagnetic radiation reflecting panel is transmitted directlytherethrough without absorption.

In FIG. 10B, the electrically-active LHCP electromagnetic radiationreflecting panel 22B is shown operated in its electrically active state(i.e. when V=1). As shown in FIG. 10D, electromagnetic radiation havinga LHCP or RHCP polarization state and any wavelength within transmissionbandwidth αλ_(transmission) ^(LHCP) is transmitted directly through theglazing panel without absorption.

The electrically-passive π-phase retardation panel 21 employed in theelectro-optical glazing structure of FIG. 10 can made from any materialhaving a permanent birefringence which imparts to a π-phase retardationto electromagnetic radiation (within the operational band of thedevice). This panel can be fabricated from PVA, nematic liquid crystal,mica, etc. in a manner well known in the art. Methods for making suchoptical devices are disclose in U.S. Pat. No. 5,113,285 to Franklin, etal., incorporated herein by reference.

Electrically-switchable circularly polarizing reflective panels 22A and22B can be fabricated using the construction techniques illustrated inFIGS. 11 through 11A3. As shown in FIG. 11, each such panel generallycomprises a pair of optically transparent plates 22A1 and 22A2 (e.g.made of glass, acrylic, etc.) spaced apart by a spacers 22A3 in a mannerknown in the art. In the illustrative embodiment, the spacing betweenthe plates is about 20 microns, however, it is understood that suchdimensions may vary from embodiment to embodiment of the invention. Theinternal surfaces of the plates are coated with a layer of ITO material22A4 and 22A to form optically transparent electrode surfaces. Apolyimide coating is applied over the ITO layers, which is then rubbedto create director (i.e. alignment) surfaces for liquid crystalmolecules to spontaneously order in accordance with the chiral phase, ina manner well known in the art. Electrical leads are attached to the ITOlayers.

Having formed a cell between the spaced apart plates 22A1 and 22A2, acholesteric liquid crystal (CLC) mixture 22A6 is prepared and thenpoured into the interior volume of the “cell” formed between the platesand spacers. In the illustrative embodiment set forth in FIG. 10, a“left-hand CLC formula” must be used to make the CLC mixture for theelectrically switchable LCHP panels 22A and 22B. In the illustrativeembodiment set forth in FIG. 12, a “right-hand CLC formula” must be usedto make the CLC mixture for the electrically switchable RCHP panels 25Aand 25B. In the illustrative embodiment set forth in FIG. 14, a“left-hand CLC formula” must be used to make the CLC mixture for theelectrically switchable LHCP panel 28A, and a “right-hand CLC formula”must be used to make the CLC mixture for the electrically switchableRHCP panel 28B. These CLC formulas will be described in detail below.

According to the left-handed CLC formula, the following materialcomponents are measured and mixed together in a vessel, in thehereinafter specified “by weight” proportions, namely: 1 weight unit ofliquid crystal polymerizable material having a left-handed cholestericorder (phase) (e.g. CC4039L from Wacker Chemical, Germany); 49.4 weightunits of low-molecular weight nematic liquid crystal material (e.g. E7from EMI, Inc. of Hawthorne, N.Y.); 0.026 weight units of UVphotointiator (e.g. IG184 from Ciba Gigy); 0.30 weight units of a firstleft-handed chiral additive (e.g. R1011 from EMI, Inc.); and 0.42 weightunits of a second left-handed chiral additive (e.g. CB15 from EMI,Inc.).

According to the right-handed CLC formula, the following materialcomponents are measured and mixed together in a vessel, in thehereinafter specified “by weight” proportions, namely: 1 weight unit ofliquid crystal polymerizable material having a right-handed cholestericorder (phase) (e.g. CC4039R from Wacker Chemical, Germany); 49.4 weightunits of low-molecular weight nematic liquid crystal material (e.g. E7from EMI, Inc. Of Hawthorne, N.Y.); 0.026 weight units of UVphotointiator (e.g. IG184 from Ciba-Gigy); 0.30 weight units of a firstright-handed chiral additive (e.g. R1011 from EMI, Inc.); and 0.42weight units of a second right-handed chiral additive (e.g. CB15 fromEMI, Inc.). The spectral reflection characteristics for this particularright-handed CLC material (prior to UV polymerization) are shown in FIG.11A1.

After the appropriate CLC mixture has been made and poured into the cellregion between the glass plates 22A1 and 22A2, the panel structure isplaced in a temperature-controlled curing cabinet containing a UV lightsource of controlled light intensity. The CLC panel structure is thencured within the cabinet. For the case of the above-describedembodiment, using the above-described CLC mixture formulas, the CLCstructure is cured for 12 hours while being maintained at 25° C. andexposed to UV light of 365 nm and power density 0.72 mW/cm².

In FIG. 11A1, the reflection characteristics of the RHCP CLC panel priorto UV polymerization are shown. In FIG. 11A2, the reflectioncharacteristics for the RHCP CLC panel after UV polymerization are shownwhen no voltage has been applied across the ITO coated plates. Notably,after UV polymerization, the reflection bandwidth of the CLC materialhas doubled. In FIG. 11A3, the reflection characteristics for the RHCPCLC panel are shown when a voltage has been applied. Notably, the bigreflection peak shown in FIG. 11A2 disappears due to the unwinding ofthe CLC helix of the CLC panel in the presence of the electric fieldcreated by the applied voltage. However, a weak peak is still observedin the reflection characteristics of this example due to the fact thatthe applied voltage had not been high sufficiently high enoughintensity.

Having constructed the various subcomponents of the electro-opticalglazing structure of FIG. 10, panels 21, 22A and 22B can then bephysically interfaced as an integral unit using conventional laminationtechniques well known in the glazing art.

The operation of the glazing structure shown in FIG. 10 will now bedescribed with reference to FIGS. 10E and 10F.

As shown in FIG. 10E, the electro-optical glazing structure of FIG. 10is switched to its optically opaque state of operation by not applying acontrol voltage thereacross (i.e. V=0). In this optical state, theelectro-optical glazing structure 20 reflects LHCP and RHCPelectromagnetic radiation within αλ_(reflection) ^(LHCP) incident oneither LHCP electromagnetic radiation reflecting panel withoutadsorption, independent of the direction of propagation thereof, asshown in FIG. 10E. As such, the operation of this particularelectro-optical glazing structure is “symmetrical”. The physicalmechanisms associated with such reflection processes are schematicallyillustrated in FIG. 10E in great detail. Inasmuch as 100% of incidentelectromagnetic radiation is transmitted through the electro-opticalglazing structure, this glazing structure is “totally reflective” inthis state of operation.

As shown in FIG. 10F, the electro-optical glazing structure of FIG. 10is switched to its optically transparent (i.e. clear) state of operationby applying the appropriate control voltage thereacross (i.e. V=1). Inthis optical state, the electro-optical glazing structure 20 transmitsboth LHCP and RHCP electromagnetic radiation within αλ_(reflection)^(LHCP) incident on either LHCP electromagnetic radiation reflectingpanel of the window panel without adsorption, independent of thedirection of propagation of the incident electromagnetic radiation. Assuch, the operation of this particular electro-optical glazing structureis “symmetrical”. The physical mechanisms associated with suchtransmission processes are schematically illustrated in FIG. 10F ingreat detail. Inasmuch as 100% of incident electromagnetic radiation istransmitted through the electro-optical glazing structure, this glazingstructure is “totally transmissive” in this state of operation.

The electro-optical glazing structure of FIG. 10 can be readily adaptedto exhibit “asymmetrical” reflection/transmission characteristics overits broad-band of operation by tuning the spectral transmissioncharacteristics of both the CLC-based LHCP electromagnetic radiationreflecting panels 22A and 22B so that the spectral reflection (andtransmission) bandwidth characteristics thereof are either completely orpartially overlapping or are separated on the wavelength (i.e.frequency) domain. Using such CLC-tuning techniques, it is possible tocreate an electro-optical glazing structure having the construction ofFIG. 10 which, when switched to its first optical state, is capable oftotally reflecting electromagnetic radiation within a desired reflectionband (e.g. within the ultraviolet and infrared bands) in a firstdirection defined with respect to the panel, and when switched to itssecond optical state, totally transmitting electromagnetic radiationwithin such reflection band.

Sixth Illustrative Embodiment of the Electro-Optical Glazing Structureof the Present Invention

The sixth illustrative embodiment of the electro-optical glazingstructure hereof will be described with reference to FIGS. 12 through13B.

As shown in FIG. 12, the electro-optical glazing structure of the sixthillustrative embodiment 24 comprises: an electrically-passive π-phaseretardation panel 21 interposed between a first electrically-active RHCPelectromagnetic radiation reflecting panel 25A and a secondelectrically-active RHCP electromagnetic radiation reflecting panel 25B;and electrically conductive means 26 for applying optical-state controlvoltages to the electrically-active RHCP electromagnetic radiationreflecting panels 25A and 25B. Preferably, the electro-optical glazingstructure of FIG. 12 is mounted within a frame structure as described inconnection with the generalized embodiment shown in FIGS. 1A and 1B, andincorporates all of the power generation, electromagnetic radiationdetection and micro-control mechanisms thereof.

In FIG. 12A, the electrically-active RHCP electromagnetic radiationreflecting panel 25A (25B) is shown being operated in its electricallyinactive state (i.e. when V=0). As shown in FIG. 12B, electromagneticradiation having a RHCP polarization state and a wavelength inside thecharacteristic reflection bandwidth αλ_(reflection) ^(RHCP) of the RHCPelectromagnetic radiation reflecting panel 25A (25B) is reflecteddirectly therefrom without absorption, while electromagnetic radiationhaving either a LHCP polarization state and/or a wavelength outside thecharacteristic reflection bandwidth αλ_(reflection) ^(RHCP) of the RHCPelectromagnetic radiation reflecting panel is transmitted directlytherethrough without absorption.

In FIG. 12C, the electrically-active RHCP electromagnetic radiationreflecting panel 25A (25B) is shown being operated in its electricallyactive state (i.e. when V=1). As shown in FIG. 12D, electromagneticradiation having a LHCP or RHCP polarization state and any wavelengthwithin transmission bandwidth αλ_(transmission) ^(RHCP) is transmitteddirectly through the electro-optical panel without absorption.

The electrically-passive π-phase retardation panel 21 employed in theelectro-optical glazing structure of FIG. 12 can be realized in themanner described above in connection with the embodiment shown in FIG.12 above. The electrically-active, broad-band LHCP electromagneticradiation reflecting panels 25A and 25B used in the glazing structure ofFIG. 10 can be made using the fabrication methods described above inconnection with the embodiment shown in FIG. 10. Physically interfacingpanels 21, 25A and 25B of the electro-optical glazing structure of FIG.12 can be achieved using conventional lamination techniques well knownin the glazing art.

The operation of the glazing structure of FIG. 12 will now be describedwith reference to FIGS. 13A and 13B.

As shown in FIG. 13A, the electro-optical glazing structure of FIG. 12is switched to its optically opaque state of operation by not applying acontrol voltage thereacross (e.g. V=0 Volts). In this optical state, theelectro-optical glazing structure 24 reflects LHCP and RHCPelectromagnetic radiation within αλ_(reflection) ^(RHCP) incident on theRHCP electromagnetic radiation reflecting panel 25A (25B) of the windowpanel without adsorption, independent of the direction of propagation ofthe incident electromagnetic radiation. As such, the operation of thisparticular electro-optical glazing structure is “symmetrical”. Thephysical mechanisms associated with such reflection processes areschematically illustrated in FIG. 13A in great detail. Inasmuch as 100%of incident electromagnetic radiation is reflected from theelectro-optical glazing structure, this glazing structure is “totallyreflective” in this state of operation.

As shown in FIG. 13B, the electro-optical glazing structure of FIG. 12is switched to its optically transparent (i.e. clear) state of operationby applying the appropriate control voltage thereacross (e.g. V=1Volts). In this optical state, the electro-optical glazing structure 24transmits both LHCP and RHCP electromagnetic radiation withinαλ_(reflection) ^(RHCP) incident on either RHCP electromagneticradiation reflecting panel 25A (or 25B) without adsorption, independentof the direction of propagation of the incident electromagneticradiation. As such, the operation of this particular electro-opticalglazing structure is “symmetrical”. The physical mechanisms associatedwith such transmission processes are schematically illustrated in FIG.13B in great detail. Inasmuch as 100% of incident electromagneticradiation is transmitted through the electro-optical glazing structure,this glazing structure is “totally transmissive” in this state ofoperation.

The electro-optical glazing structure of FIG. 12 can be readily adaptedto exhibit “asymmetrical” reflection/transmission characteristics overits broad-band of operation by tuning the spectral transmissioncharacteristics of both the CLC-based RHCP electromagnetic radiationreflecting panels 25A and 25B so that the spectral reflection (andtransmission) bandwidth characteristics thereof are either completely orpartially overlapping or are separated on the wavelength (i.e.frequency) domain. Using CLC-tuning techniques, it is possible to createan electro-optical glazing structure having the construction of FIG. 12which, when switched to its first optical state, is capable of totallyreflecting electromagnetic radiation within a desired reflectionbandwidth (e.g. within the ultraviolet and infrared bands) in adirection defined with respect to the panel, and when switched to itssecond optical state, totally transmitting electromagnetic radiationwithin such reflection band.

Seventh Illustrative Embodiment of the Electro-Optical Glazing Structureof the Present Invention

The seventh illustrative embodiment of the electro-optical glazingstructure hereof will be described with reference to FIGS. 14 through15B.

As shown in FIG. 14, the electro-optical glazing structure of theseventh illustrative embodiment 27 comprises: an electrically-activeLHCP electromagnetic radiation reflecting panel 28A; anelectrically-active RHCP electromagnetic radiation reflecting panel 28Blaminated to panel 28A; and electrically conductive means 29 forapplying optical-state control voltages to the electrically-active LHCPand RHCP electromagnetic radiation reflecting panels 28A and 28B.Preferably, the electro-optical glazing structure of FIG. 14 is mountedwithin a frame structure as described in connection with the generalizedembodiment shown in FIGS. 1A and 1B, and incorporates all of the powergeneration, electromagnetic radiation detection and micro-controlmechanisms thereof.

In FIG. 14A, the electrically-active LHCP electromagnetic radiationreflecting panel 28A is shown being operated in its electricallyinactive state (i.e. when V=0). As shown in FIG. 14B, electromagneticradiation having a LHCP polarization state and a wavelength inside thecharacteristic reflection bandwidth αλ_(reflection) ^(LHCP) of the LHCPelectromagnetic radiation reflecting panel 28A is reflected directlytherefrom without absorption, while electromagnetic radiation havingeither a RHCP polarization state and/or a wavelength outside thecharacteristic reflection bandwidth αλ_(reflection) ^(LHCP) of the LHCPelectromagnetic radiation reflecting panel 28A is transmitted directlytherethrough without absorption.

In FIG. 14C, the electrically-active LHCP electromagnetic radiationreflecting panel 28B is shown being operated in its electrically activestate (i.e. when V=1). As shown in FIG. 14D, electromagnetic radiationhaving a LHCP or RHCP polarization state and any wavelength withintransmission bandwidth αλ_(reflection) ^(LHCP) is transmitted directlythrough the electro-optical panel 28A without absorption.

In FIG. 14E, the electrically-active RHCP electromagnetic radiationreflecting panel 28B is shown being operated in its electricallyinactive state (i.e. when V=0). As shown in FIG.14F, electromagneticradiation having a RHCP polarization state and a wavelength inside thecharacteristic reflection bandwidth αλ_(reflection) ^(RHCP) of the RHCPelectromagnetic radiation reflecting panel 28B is reflected directlytherefrom without absorption, while electromagnetic radiation havingeither a LHCP polarization state and/or a wavelength outside thecharacteristic reflection bandwidth αλ_(reflection) ^(RHCP) of the RHCPelectromagnetic radiation reflecting panel 28B is transmitted directlytherethrough without absorption.

In FIG. 14G, the electrically-active RHCP electromagnetic radiationreflecting panel 28B is shown being operated in its electrically activestate (i.e. when V=1). As shown in FIG. 14H, electromagnetic radiationhaving a LHCP or RHCP polarization state and any wavelength withintransmission bandwidth αλ_(transmission) ^(RHCP) is transmitted directlythrough the electro-optical panel 28B without absorption.

The electrically-active, broad-band LHCP and RHCP electromagneticradiation reflecting panels 28A abd 28B used in the glazing structure ofFIG. 14 can be made using the fabrication methods described above inconnection with the embodiment shown in FIG. 10. In the preferredembodiment, the liquid crystal polymer material contained within panel28A can be made using the following formula: CLC polymer (BASF 171):12%; CB15: 25%; E44: 64%; IG184: 1%. The sample is made by filling themixture into a pair of buffed polyimide ITO glass substitutes. UVcurving intensity is 10⁵ w/cm². A similar formula is used to make theliquid crystal polymer material contained within panel 28B.

Physically interfacing panels 28A and 28B of the electro-optical glazingstructure of FIG. 14 can be achieved using conventional laminationtechniques well known in the glazing art.

The operation of the glazing structure of FIG. 14 will now be describedwith reference to FIGS. 15A and 15B.

As shown in FIG. 15A, the electro-optical glazing structure of FIG. 14is switched to its optically opaque state of operation by not applying acontrol voltage thereacross (i.e. V=0). In this optical state, theelectro-optical glazing structure 27 reflects LHCP and RHCPelectromagnetic radiation within reflection bandwidth αλ_(reflection)^(LHCP) incident on the LHCP electromagnetic radiation reflecting panel28A without adsorption, while reflecting LHCP and RHCP electromagneticradiation within reflection bandwidth αλ_(reflection) ^(RHCP) incidenton the RHCP electromagnetic radiation reflecting panel 28B withoutadsorption. As such, the operation of this particular electro-opticalglazing structure is “symmetrical”. The physical mechanisms associatedwith such reflection processes are schematically illustrated in FIG. 15Ain great detail. Inasmuch as 100% of incident electromagnetic radiationis reflected from the electro-optical glazing structure, this glazingstructure is “totally reflective” in this state of operation.

As shown in FIG. 15B, the electro-optical glazing structure of FIG. 14is switched to its optically transparent (i.e. clear) state of operationby applying the appropriate control voltage thereacross (i.e. V=1).Assuming that the LHCP electromagnetic radiation reflecting panel 28Aand RHCP electromagnetic radiation reflecting panel 28B each have thesame characteristic transmission bandwidth (i.e αλ_(transmission)^(LHCP) is the same as αλ_(transmission) ^(RHCP)), then when switched inthis optical state, the electro-optical glazing structure of FIG. 14transmits without adsorption, both LHCP and RHCP wavelengths withintransmission bandwidth αλ_(transmission) ^(LHCP) independent of whethersuch wavelengths fall incident on either the LHCP or RHCPelectromagnetic radiation reflecting panel of the electro-opticalglazing structure. As such, the operation of this particular embodimentof the electro-optical glazing structure is “symmetrical”. The physicalmechanisms associated with such transmission processes are schematicallyillustrated in FIG. 15B in great detail. Inasmuch as 100% of incidentelectromagnetic radiation is transmitted through the electro-opticalglazing structure, this glazing structure is “totally transmissive” inthis state of operation.

Notably, the electro-optical glazing structure of FIG. 14 can be readilyadapted to exhibit “asymmetrical” reflection/transmissioncharacteristics over its broad-band of operation. Such characteristicscan be imparted by tuning the spectral transmission characteristics ofboth the CLC-based RHCP and LHCP electromagnetic radiation reflectingpanels 28A and 28B of the present invention so that the spectralcharacteristics thereof are either completely or partially overlappingor are separated on the wavelength (or frequency) domain. UsingCLC-tuning techniques disclosed in International Publication No. WO97/16762, it is possible to create an electro-optical glazing structurewhich, when switched to its first optical state, is capable of totallyreflecting electromagnetic radiation within a desired reflectionbandwidth (e.g. within the UV and IR bands) in a direction defined withrespect to the panel, and when switched to its second optical state,totally transmitting electromagnetic radiation within the reflectionband.

Alternatively, the electrically-active LHCP and RHCP reflecting panels28A and 28B panels in the glazing structure of FIG. 14 can be realizedusing the novel electro-optical construction schematically illustratedin FIGS. 16A and 16B.

As shown in FIGS. 16A and 16B, the physical construction of thisalternative embodiment of the electrically-switchable broad-band CLCpanels 28A (28B) is very similar to that of the panels described abovein connection with FIGS. 11 through 11A3. However, in this alternativeembodiment shown in FIGS. 16A and 16B, the broad-band (or superbroad-band) CLC material contained between glass plates thereof isradically different from that contained with the panel illustrated inFIGS. 11 through 11A3, as will be explained below.

The novel material contained between the plates of this novelelectrically-switchable super-broadband CLC (BBCLC) polarizer is madefrom polymerizable liquid crystal blends in cholesteric order. Accordingto this aspect of the present invention, “functional pigment suspendedliquid crystal” (FPSLC) material is created by mixing (i) broad-band CLCpigments (e.g. CLC microflakes taught in International Publication No.WO 97/16762) into (ii) an electrically-active (i.e.electrically-responsive) carrier fluid such as a low-molecular weight(LMW) nematic liquid crystal fluid (e.g. E7 and E44) which iscommercially available from EMI of Hawthorne, N.Y. As will be explainedin greater detail hereinafter, the micro-sized functional pigments ofthis particular embodiment have unique optical properties that can beexploited in various applications including electro-optical glazingstructures. In the illustrative embodiment, the functional pigments arerealized using BBCLC microflakes having a size in the range of about20-100 microns. When making the LHCP panel 28A, left-handed BBCLCmicroflakes should be used, whereas when making the RHCP panel 28B,right-handed BBCLC microflakes should be used. The mass density of theCLC microflakes should be substantially equal to the mass density of theLMW carrier liquid fluid. Also the refractive index of the CLCmicroflakes should be matched closely to the refractive index of thecarrier fluid.

Once prepared, the FPSLC mixture is poured into a cell constructed froma pair of spaced apart ITO-coated glass or plastic plates. To achievethe required liquid crystal alignment, the ITO layers are coated withrubbed polyimide in a manner well known in the art. The ITO layers arealso provided with electrical leads so that an external field can beimpressed across the ITO coated glass plates. As will be illustratedgreater detail below, this makes the FPSLC material between the plateselectrically-active or switchable between its electro-optical states ofoperation. Notably, when making such electrically-switchable plates,there is no UV polymerization step, as in the above-describedfabrication methods.

After the filling operation, the CLC pigments are uniformly distributedinside the cell in order to cover the entire cell area. The cellthickness is designed to be larger than the pigment dimension. It isassumed that the liquid crystal molecules are spontaneously aligned inhomogeneous state due to the surface coating. The homogeneous alignmentof the host LC molecules forces the CLC pigments to align parallel tothe cell surface, as shown in FIG. 16A. The switching or reorientationof the host liquid crystal molecules by an applied electric field forcesthe suspended CLC pigments to be reoriented accordingly, as shown inFIG. 16B. For purposes of convention, it will be helpful to designatestate “A” of the host liquid crystal as the state when there is noelectrical field is applied, as illustrated in FIG. 16A. Accordingly,the CLC pigments are assigned to be in state “A_(c/c)”. Once a strongenough field, e.g., an electric field, is applied, the host liquidcrystal molecules are reoriented to state “B” as shown in FIG. 16B.Accordingly, the CLC pigments are reoriented from state “A_(c/c)” tostate “B_(c/c)”. Since the BBCLC pigments in the host liquid crystalpreserve the same polarization property, then its parallel orientationshould exhibit a polarizing state for an incoming light onto the cellsurface. If the CLC microflakes are vertically aligned due to thereorientation of the host liquid crystal molecules under an appliedfield, then the cell loses the capability to polarize light and becomestransparent or quasi-transparent, i.e. provided that the thickness ofthe CLC microflakes is much smaller than the aerial dimension of theelectro-optical cell.

The electrically-switchable circularly polarizing panels of the typeshown in FIGS. 16A and 16B can be realized in a variety ofconfigurations. These alternative configurations will be describedbelow.

Parallel-To-Vertical Configuration (Case I)

In this configuration, the cell is constructed so that the host nematicliquid crystal adopts a spontaneous alignment in homogeneous state. TheITO substrate is coated with a polyimide favorable for such an alignmentfollowed by a mechanical rubbing. If the host liquid crystal has apositive dielectric anisotropy, it can be vertically reoriented into ahomeotropic state by an electric field (E-field). In this case, state“A” of the host LC refers to homogeneous, and state “B” to homeotropic;while state “A_(c/c)” and “B_(c/c)” of the CLC pigments refers toparallel and perpendicular to the cell surface, respectively, asschematically shown in FIG. 16A. In this way, the panel can be switchedfrom polarizing reflection to transparent or quasi-transparent state.Varying the strength of the E-field can change the final reflectivity ofthe panel. It should be pointed out that rubbed polyimide is not theonly choice for surface treatment. Other techniques are also applicable,such as oblique deposition of SiOx, UV alignable layers, etc.

Parallel-To-Vertical Configuration (Case II)

In this configuration, the cell is constructed so that the host lowmolecular weight (LMW) cholesteric liquid crystal adopts a spontaneousalignment in the planar state. The pitch of the LMW CLC can be tunedeither inside or outside of the CLC pigment reflection spectral region.The ITO substrate is coated with a rubbed polyimide favorable for planaralignment. If the host liquid crystal in cholesteric order has apositive dielectric anisotropy, it can be reoriented vertically into ahomeotropic state by an electric field (E-field). In this case, state“A” of the host LC refers to planar, and state “B” to homeotropic; whilestate “A_(c/c)” and “B_(c/c)” of the CLC pigments refers to parallel andperpendicular to the cell surface, respectively. Thus the panel can beswitched from polarizing reflection to transparent state. Varying thestrength of the E-field can change the final reflectivity of the panel.It should be pointed out that rubbed polyimide is not the only choicefor surface treatment. Other techniques are applicable, such as obliquedeposition of SiOx, UV alignable layers, etc. In some cases, noalignment layer is required.

Vertical-To-Parallel Configuration (Case I)

In this configuration, the cell is constructed so that the host nematicliquid crystal adopts a spontaneous alignment in homeotropic state. TheITO substrate is coated with an alignment agent favorable for such analignment. No mechanical rubbing is necessary. If the host liquidcrystal has a negative dielectric anisotropy, it can be reoriented intoa homogeneous state by an electric field (E-field). In this case, state“A” of the host LC refers to homeotropic, and state “B” to homogeneous;while state “A_(c/c)” and “B_(c/c)” of the CLC pigments refer toperpendicular and parallel to the cell surface, respectively. Thus thepanel can be switched from transparent to polarizing reflection state.Varying the strength of the E-field can change the final reflectivity ofthe panel.

Vertical-To-Parallel Configuration (Case II)

In this configuration, the cell is constructed so that the host lowmolecular weight (LMW) cholesteric liquid crystal adopts a spontaneousalignment in homeotropic state. The pitch of the LMW CLC can be tunedeither inside or outside of the CLC pigment reflection spectral region.The ITO substrate is coated with an alignment agent favorable forhomeotropic alignment. If the host liquid crystal in cholesteric orderhas a negative dielectric anisotropy, it can be reoriented into a planarstate by an electric field (E-field). In this case, state “A” of thehost LC refers to homeotropic, and state “B” to planar; while state“A_(c/c)” and “B_(c/c)” of the CLC pigments refers to perpendicular andparallel to the cell surface, respectively. Thus the panel can beswitched from transparent to polarizing reflection state. Varying thestrength of the E-field can change the final reflectivity of the panel.

FPSLC with Polymer Network

In this preferred configuration, the cell is constructed so that thehost low molecular weight (LMW) liquid crystal in cholesteric ordercontains a small amount of polymer network which is formed by UVpolymerizing a polymer material mixed inside the LMW LC in absence ofany field. The purpose of introducing the polymer network is to realizea bistable state, i.e., weak scattering state and high reflection stateof the panel and, possibly, improving the reflectivity. The polymernetwork helps to better confine CLC flakes in a preferred orientation,for example, a parallel orientation. The host liquid crystal can adopteither an ECB or TN or STN or cholesteric order. The ITO substrate iscoated with a polyimide favorable for a homogeneous alignment. If thehost liquid crystal in cholesteric order has a positive dielectricanisotropy, it can be reoriented from planar to homeotropic state by anelectric field (E-field). In this case, state “A” of the host LC refersto homogeneous, and state “B” to homeotropic; while state “A_(c/c)” and“B_(c/c)” of the CLC pigments refers to parallel and perpendicular tothe cell surface, respectively. Thus the panel can be switched frompolarizing reflection to semi-or total transparent state. Varying thestrength of the E-field can change the final reflectivity of the panel.Another important feature of this polymer stabilized FPSLC configurationis that a reflection and scattering mixed mode can be realized byproperly controlling polymer density and applied voltage, similar to theconventional polymer stabilized cholesteric texture (PSCT).

FPSLC with Surface Stabilization Function

In this preferred configuration, the cell is constructed so that thehost low molecular weight (LMW) liquid crystal in cholesteric order issurface stabilized which exhibits also a bistable state, i.e., weakscattering state and relatively high reflective state. This texturehelps to better confine CLC flakes in a preferred orientation, forexample, a parallel orientation. The ITO substrate is coated with apolyimide favorable for a homogeneous alignment. If the host liquidcrystal in cholesteric order has a positive dielectric anisotropy, itcan be reoriented from planar to homeotropic state by an electric field(E-field). In this case, state “A” of the host LC refers to homogeneous,and state “B” to homeotropic; while state “A_(c/c)” and “B_(c/c)” of theCLC pigments refers to parallel and perpendicular to the cell surface,respectively. Thus the panel can be switched from polarizing reflectionto semi-or total transparent state. Varying the strength of the E-fieldcan change the final reflectivity of the panel. Another importantfeature of this surface-stabilized FPSLC configuration is that areflection and scattering mixed mode can be realized by properlycontrolling polymer density and applied voltage, similar to theconventional polymer stabilized cholesteric texture (PSCT).

Each of the cell configurations described above can be used to build aswitchable (super) broadband FPSLC panel which is electricallyswitchable from reflection state to transparent state, or vice versa.The reflected light is polarized and can cover a broad spectralbandpass, such as the entire visible region. Ideally, in a perfectreflection state, 50% of the incident light is reflected into onepolarization state and another 50% is transmitted in other polarizationstate. However, when switched into the total transmission mode, thepanel passes 100% of the incident light. Varying the strength of theE-field can change the final reflectivity between 0% and 50%(equivalently, the transmittance can be varied between 50% to 100%).

The electrically-switchable FPSLC-based structures described above canbe used to realize the electrically-switchable circularly polarizingpanels employed in the systems shown in FIGS. 10 and 12 hereof. In suchelectro-optical glazing structures, the particular compositions used tocreated the FPSLC material will vary in order to provide the requiredpolarization reflective functions. For example, when making broad-bandLHCP panels 22A and 22B, left-handed BBCLC microflakes should be addedto the LMW liquid crystal carrier fluid of the FPSLC mixture thereof.When making broad-band RHCP panels 25A and 25B, right-handed BBCLCmicroflakes should be added to the LMW liquid crystal carrier fluid ofthe FPSLC mixture thereof. When making RHCP panels 25A and 25B havingspectrally-tuned reflection characteristics, right-handed BBCLCmicroflakes with narrow-band reflection characteristics should be addedto the LMW liquid crystal carrier fluid of the FPSLC mixture thereof.For example, five color CLC microflakes (i.e. pigments) can be addedinto the LMW liquid crystal carrier fluid in order to cover the visibleband. It is understood, various combinations of left and right handedCLC microflakes (having super broad-band, broad-band and/or narrow-bandpolarization reflection characteristics) can be added to the LMW liquidcrystal carrier fluid in order to produce electrically-switchablecircularly polarizing glazing structures having diverse polarizationreflection characteristics adapted to meet any application imaginable.

Additional Embodiments of the Electro-Optical Glazing Structure of thePresent Invention

Many more embodiments of the electro-optical glazing structure of thepresent invention can be provided by combining the above-describedembodiments so provide systems and devices having transmission andreflection modes of operation.

In particular, the illustrative embodiments of the invention disclosedin FIGS. 2 through 9B and FIGS. 14 through 15B, in particular, can bereadily combined with other structures to provide additional embodimentsof the present invention. For simplicity of explanation, the embodimentsdescribed hereinabove are generalized in FIGS. 21 through 23F.

In paricular, FIGS. 21 through 21F provide a generalized description ofthe illustrative embodiments disclosed in FIGS. 6 and 8, wherein theelectrically-passive broad-band polarizing layers have differenthandedness in both the circularly polarizing (RHCP/LHCP) and linearlypolarizing (LP1/LP2) system configurations. FIGS. 22 through 22F providea generalized description of the illustrative embodiments disclosed inFIGS. 2 and 4, wherein the electrically-passive broad-band polarizinglayers have the same handedness in both the circularly polarizing(LHCP/LHCP or RHCP/RHCP) and linearly polarizing (LP1/LP1 or LP2/LP2)system configurations. Before describing these additional embodiments ofthe electro-optical glazing structure hereof, the operation of these twogeneralized embodiments of the present invention will be brieflysummarized. Likewise, FIGS. 23 through 23F provide a generalizeddescription of the illustrative embodiment disclosed in FIGS. 14 through15B, wherein the electrically-active broad-band polarizing layers have adifferent handedness in the circularly polarizing (LHCP/LHCP orRHCP/RHCP) system configurations, and there is no otpically activeelement disposed between the electrically-active polarizing layers.

Before describing additional embodiments of the electro-optical glazingstructure hereof which can be based on the above-indentifiedembodiments, it will be helpful to briefly summarize the structure andfunction of these embodiments hereinbelow in a more generalized mannerto more clearly appreciate the various aspects of the present invention.

In FIG. 21A, the electro-optical glazing structure of FIG. 21 is shownoperated in its partial-reflection/transmission mode, wherein noexternal voltage (i.e. V=V_(off)) is applied to the π phase shifter. InFIGS. 21B and 21C, transmission and reflection characteristics for thismode of operation are shown, respectively. In FIG. 21D, theelectro-optical light glazing structure of FIG. 21 is shown operated inits total-reflection mode, wherein an external voltage V (i.e. V=V_(on))is applied to the π phase shifter. In FIGS. 21E and 21F, transmissionand reflection characteristics for this mode of operation are shown,respectively.

In FIG. 22A, the electro-optical glazing structure of FIG. 22 is shownoperated in its total-reflection mode, wherein no external voltage (i.e.V=V_(off)) is applied to the π phase shifter. In FIGS. 22B and 22C,transmission and reflection characteristics for this mode of operationare shown, respectively. In FIG. 22D, the electro-optical light glazingstructure of FIG. 22 is shown operated in itspartial-reflection/transmission mode, wherein an external voltage V(i.e. V=V_(on)) is applied to the π phase shifter. In FIGS. 22E and 22F,transmission and reflection characteristics for this mode of operationare shown, respectively.

In FIG. 23A, the electro-optical glazing structure of FIG. 23 is shownoperated in its total-reflection mode, wherein no external voltage (i.e.V=V_(off)) is applied to the π phase shifter. In FIGS. 23B and 23C,transmission and reflection characteristics for this mode of operationare shown, respectively. In FIG. 23D, the electro-optical light glazingstructure of FIG. 23 is shown operated in its total-transmission mode,wherein an external voltage V (i.e. V=V_(on)) is applied to the π phaseshifter. In FIGS. 23E and 23F, transmission and reflectioncharacteristics for this mode of operation are shown, respectively.

In FIG. 24, an other illustrative embodiment of the electro-opticalglazing structure of the present invention is shown comprising: a firstelectrically-passive broadband IR reflective polarizing panel forreflecting incident LHCP light within the broad IR band, andtransmitting all other components of light; a secondelectrically-passive broadband IR reflective polarizing panel, laminatedor mounted to the first IR reflective polarizing panel, for reflectingincident RHCP light within the broad IR band, and transmitting all othercomponents of light. The resulting IR filter structure is mounted oraffixed to an electrically-controlled light scattering panel, forselectively scattering light over the visible band (when no externalvoltage is applied) so as to render the resulting glazing structureopaque to provide privacy behind the window structure into which isinstalled. While circularly polarizing reflectors of the type taught inInternaational Publication No WO/97/16762 by Reveo, Inc., incorporatedherein by reference, can be used to realize the broad-band IRcircularly-polarizing panels of this structure, it is understood thatbroad-band IR polarizers which reflect linearly polarized light, astaught in International Application No. PCT/US97/20091 by Reveo, Inc.,incorporated herein by reference, may also well be used to realize suchlinearly polarizing IR panels. Alternatively, such broadband IRreflecting panels may be made from multilayer polymer layers asdisclosed in U.S. Pat. No. 5,686,979, incorporated herein by reference,and as taught elsewhere in the prior art. The electrically-controlledlight scattering panel employed in the glazing structure of FIG. 24 canbe realized by any one of the electrically-controlled light scatteringpanels disclosed in FIGS. 17A through 20F, described in detailhereinbelow.

In FIG. 24A, the electro-optical glazing structure of FIG. 24 is shownoperated in scattering mode, wherein no external voltage (i.e.V=V_(off)) is applied to the electrically-controlled scattering panel.In FIGS. 24B and 24C, transmission and reflection characteristics forthis mode of operation are shown, respectively. During this stateoperation, the composite broad-band IR structure totally reflectsincident IR radation providing excellent thermal insulation to theglazing structure, while the electrically-controlled scattering panelrenders the glazing structure optically opaque over the visible-band ofthe spectrum. In FIG. 24D, the electro-optical light glazing structureof FIG. 24 is shown operated in its total-transmission mode, wherein anexternal voltage V (i.e. V=V_(on)) is applied to electrically-controlledlight scattering panel. In FIGS. 24E and 24F, transmission andreflection characteristics for this mode of operation are shown,respectively. During this state operation, the composite broad-band IRstructure totally reflects incident IR radation providing excellentthermal insulation to the glazing structure, while theelectrically-controlled scattering panel renders the glazing structureoptically transparent over the visible-band of the spectrum enablingviewing through the glazing structure in bi-directional manner.

In FIG. 25, an other illustrative embodiment of the electro-opticalglazing structure of the present invention is shown. This is the reversemode of the electro-optical glazing structure shown in FIG. 24. Asshown, this glazing structure comprises: a first electrically-passivebroadband IR reflective polarizing panel for reflecting incident LHCPlight within the broad IR band, and transmitting all other components oflight; a second electrically-passive broadband IR reflective polarizingpanel, laminated or mounted to the first IR reflective polarizing panel,for reflecting incident RHCP light within the broad IR band, andtransmitting all other components of light. As shown, the resulting IRfilter structure is mounted or affixed to an electrically-controlledlight scattering panel, for selectively scattering light over thevisible band (when an external voltage is applied) so as to render theresulting glazing structure opaque to provide privacy behind the windowstructure into which is installed. While circularly polarizingreflectors of the type taught in Internaational Publication NoWO/97/16762 by Reveo, Inc., incorporated herein by reference, can beused to realize the broad-band IR circularly-polarizing panels of thisstructure, it is understood that broad-band IR polarizers which reflectlinearly polarized light, as taught in PCT Application No.PCT/US97/20091 by Reveo, Inc., incorporated herein by reference, mayalso well be used to realize such linearly polarizing IR panels.Alternatively, such broadband IR reflecting panels may be made frommultilayer polymer layers as are know in the art. Alternatively, suchbroadband IR reflecting panels may be made from multilayer polymerlayers as disclosed in U.S. Pat. No. 5,686,979, incorporated herein byreference, and as taught elsewhere in the prior art. Theelectrically-controlled light scattering panel employed in the glazingstructure of FIG. 24 can be realized by any one of theelectrically-controlled light scattering panels disclosed in FIGS. 17Athrough 20F, described in detail hereinbelow.

In FIG. 25A, the electro-optical glazing structure of FIG. 25 is shownoperated in its light transmission mode, wherein no external voltage(i.e. V=V_(off)) is applied to the electrically-controlled scatteringpanel. In FIGS. 25B and 25C, transmission and reflection characteristicsfor this mode of operation are shown, respectively. During this stateoperation, the composite broad-band IR structure totally reflectsincident IR radation providing excellent thermal insulation to theglazing structure, while the electrically-controlled scattering panelrenders the glazing structure substantially transparent over thevisible-band of the spectrum. In FIG. 25D, the electro-optical lightglazing structure of FIG. 24 is shown operated in its light scatteringmode, wherein an external voltage V (i.e. V=V_(on)) is applied toelectrically-controlled light scattering panel. In FIGS. 25E and 25F,transmission and reflection characteristics for this mode of operationare shown, respectively. During this state operation, the compositebroad-band IR structure totally reflects incident IR radation providingexcellent thermal insulation to the glazing structure, while theelectrically-controlled scattering panel renders the glazing structureoptically opaque over the visible-band of the spectrum preventingviewing through the glazing structure.

In FIG. 26, another embodiment of the electro-optical glazing structureof the present invention is disclosed. As shown, this electro-opticalstructure is constructed by adding the broad-band IR filter panel shownin FIGS. 24 and 25, to the electro-optical glazing structure shown inFIG. 22 wherein the broadband polarizing panels are each of the samehandedness (e.g. RHCP/RHCP or LP1/LP1).

In FIG. 26A, the electro-optical glazing structure of FIG. 26 is shownoperated in its total-transmission mode, wherein no external voltage(i.e. V=V_(off)) is applied to the π phase shifting panel disposedbetween the pair of broadband polarizing reflective panels thereof. InFIGS. 26B and 26C, transmission and reflection characteristics for thismode of operation are shown, respectively. During this state operation,the composite broadband IR filter structure totally reflects incident IRradation providing excellent thermal insulation to the glazingstructure, while the electro-optical glazing substructure (shownindividually in FIG. 22) totally-reflects over the visible band in orderto render the glazing structure substantially transparent over thevisible-band of the spectrum. In FIG. 26D, the electro-optical lightglazing structure of FIG. 26 is shown operated in itspartial-reflection/transmission mode, wherein an external voltage V(i.e. V=V_(on)) is applied to the π phase shifting panel disposedbetween the pair of broadband polarizing reflective panels thereof. InFIGS. 26E and 26F, transmission and reflection characteristics for thismode of operation are shown, respectively. During this state operation,the composite broad-band IR filter structure totally reflects incidentIR radation providing excellent thermal insulation to the glazingstructure, while the electro-optical glazing substructure (shownindividually in FIG. 22) renders the glazing structure optically opaqueover the visible-band of the spectrum preventing viewing through theglazing structure.

In FIG. 27, another embodiment of the electro-optical glazing structureof the present invention is disclosed which is operates in the “reverse”mode of the glazing structure of FIG. 26, described above. As shown inFIG. 27, this electro-optical structure is constructed by adding thebroad-band IR filter panel shown in FIGS. 24 and 25, to theelectro-optical glazing structure shown in FIG. 21 wherein the broadbandpolarizing panels are each of different handedness (e.g. RHCP/LHCP orLP1/LP2).

In FIG. 27A, the electro-optical glazing structure of FIG. 27 is shownoperated in its partial-reflection/transmission mode, wherein noexternal voltage (i.e. V=V_(off)) is applied to the π phase shiftingpanel disposed between the pair of broadband polarizing reflectivepanels thereof. In FIGS. 27B and 27C, transmission and reflectioncharacteristics for this mode of operation are shown, respectively.During this state operation, the composite broadband IR filter structuretotally reflects incident IR radation providing excellent thermalinsulation to the glazing structure, while the electro-optical glazingsubstructure (shown individually in FIG. 21) partially-reflects andpartially-transmitts over the visible band in order to render theglazing structure semi-opaque over the visible-band of the spectrum. InFIG. 27D, the electro-optical light glazing structure of FIG. 27 isshown operated in its total-reflection mode, wherein an external voltageV (i.e. V=V_(on)) is applied to the π phase shifting panel disposedbetween the pair of broadband polarizing reflective panels thereof. InFIGS. 27E and 27F, transmission and reflection characteristics for thismode of operation are shown, respectively. During this state operation,the composite broad-band IR filter structure totally reflects incidentIR radation providing excellent thermal insulation to the glazingstructure, while the electro-optical glazing substructure (shownindividually in FIG. 21) renders the glazing structure optically opaqueover the visible-band of the spectrum preventing viewing through theglazing structure.

In FIG. 28, another embodiment of the electro-optical glazing structureof the present invention is disclosed. As shown, this electro-opticalstructure is constructed by adding the broad-band IR filter panel shownin FIGS. 24 and 25, to the electro-optical glazing structure shown inFIG. 23, wherein the electrically-active broadband polarizing panelsthereof are each of different handedness (i.e. RHCP/LHCP).

In FIG. 28A, the electro-optical glazing structure of FIG. 28 is shownoperated in its total-reflection mode, wherein no external voltage (i.e.V=V_(off)) is applied to the electrically-active circularly-polarizingreflective panels thereof. In FIGS. 28B and 28C, transmission andreflection characteristics for this mode of operation are shown,respectively. During this state operation, the composite broadband IRfilter structure totally reflects incident IR radation providingexcellent thermal insulation to the glazing structure, while theelectro-optical glazing substructure (shown individually in FIG. 21)totally-reflects over the visible band in order to render the glazingstructure optically opaque over the visible-band of the spectrum. InFIG. 28D, the electro-optical light glazing structure of FIG. 26 isshown operated in its total-transmission mode, wherein an externalvoltage V (i.e. V=V_(on)) is applied to the electrically-activecircularly-polarizing reflective panels thereof. In FIGS. 28E and 28F,transmission and reflection characteristics for this mode of operationare shown, respectively. During this state operation, the compositebroad-band IR filter structure totally reflects incident IR radationproviding excellent thermal insulation to the glazing structure, whilethe electro-optical glazing substructure (shown individually in FIG. 22)renders the glazing structure optically transparent over thevisible-band of the spectrum.

FIGS. 29A through 29C show a broad-band reflector for use inconstructing broad-band circularly (and linearly) polarizing reflectivepanels employed in any one of embodiments of the electro-optical glazingpanel hereof.

FIG. 29A shows a multilayer extruded polymer layer comprising a numberof pairs of layers. Each layer of a pair has a different index ofrefraction from the other layer of the pair. The various layers are ofthe order of a quarter wavelength of light, so than the electric fieldof the light reflecting from the layer boundaries adds in phase withlight reflecting from other boundaries to increase reflection in a wellknown manner.

FIG. 29B shows the prior art distribution of the layer thicknesses. Thethickness of the layers does not change with depth, changes in stepwisefashion, or changes in a linear fashion. FIG. 29C shows a non-linearchange in the thickness of the layers with depth. As taught inInternational Publication No. WO/97/16762 by Reveo, Inc., a non linearlyvarying pitch is necessary for efficient broad band reflection fromcholesteric liquid crystal material. The non-linearly varying pitchshown in FIG. 29C allows much broader range of reflectivity than theprior art pitch variations of FIG. 29B for the multilayer reflectors. Inthe case that the two polymer layers shown in FIG. 29A are layers of atleast one birefringent material where the index of refraction for afirst linear polarization is changed from one material to the next, butwhere the index of refraction for a second linear polarizationperpendicular to the first is the same from one material to the next,the structure shown in FIG. 29A will reflect light of the firstpolarization, and transmit light of the second polarization. Thenon-linearly varying pitch shown by FIG. 29C ensures broad bandoperation of the device without interference effects at shorterwavelengths which plague the step function distribution attempt atbroadband operation of the prior art.

Broad band IR reflectors made from the multilayer extruded polymermaterial shown in FIG. 29A may be added to the panels of the inventionto add IR reflectivity to the control of visible light. Multilayerlinear polarizers may be used in the panels of the invention instead ofCLC materials for controlling the light.

Additional Embodiments of the Electro-Optical Glazing Structure of thePresent Invention

Each of illustrative embodiments of electro-optical glazing panel hereofdescribed hereinabove can be combined in various ways in order toprovide intelligent glazing structures capable of controlling lighttransmission therethrough in any number of radiation bands. For example,transmission in the IR band may be allowed in the winter in thedaylight, and at night the IR light may be reflected to save heatingenergy. In summer, however, IR light may be allowed to escape from thewindow structure, while visible radiation is reflected to insureprivacy.

While the intelligent glazing structures of the invention taughthereinabove allow a very large part of the visible spectrum to besubstantially totally reflected, some of these embodiments may, inpractice, transmit some radiation, especially at large angles measuredwith respect to a projection axis normal to the glazing structure, orallow a very small amount of light to leak from a brightly lit room atnight, to the dark outside. Consequently, such undesired lighttransmission in such instances may compromise the level of privacydemanded by particular users in diverse lighting environments.Therefore, there is a great need for a way to further improve theabove-described electro-optical glazing structures of the presentinvention in a simple yet effective manner.

In accordance with another aspect of the present invention, this problemof undesired, partial light transmission can be solved, in instanceswhere it arises, by embodying each electro-optical glazing structure ofthe present invention with an additional structure that is capable ofcontrolling (e.g. reflecting or scattering) light incident thereon so asto either block the transmission of such light by reflection, or obscureit by scattering. In principle, such objectives can be achieved using avariety of different types of electro-optical structures well known inthe art for different purposes, unrelated to the above-described problemat hand. The improved electro-optical glazing structures can be formedby mounting or incorporting such electrically-controllable structures toany of the above-described electro-optical glazing structures. Inprinciple, such alternative embodiments of the present invention shouldsolve the problems associated with partial light transmission duringreflection modes of operation of the panel, thereby ensuring the desiredlevel of privacy demanded by its user in diverse environments. Severaldifferent embodiments of the light controlling (reflecting orscattering) structure are described hereinbelow.

In FIGS. 17A and 17B, a first illustrative embodiment of theelectrically-controllable light scattering structure is shown in theform of an ultra-thin panel comprising a polymer dispersed liquidcrystal (PDLC) material 173 contained between a pair of spaced-aparttransparent electrically conducting layers 174 and 175 (e.g. ITO). ThePDLC material comprises a polymer material with regions 176 of liquidcrystal material formed into small spheres of micron or submicrondimension. As illustrated in FIG. 17A, the molecules of the liquidcrystal material (depicted as short lines) are correlated by theinternal forces in the liquid crystal to have internal order, which mayrandom in a predetermined state of the panel.

In FIG. 17A, PDLC panel 172 is shown operated in its scattering state,wherein light rays 171 incident on a layer 172 are scattered by theliquid crystal molecules ordered therein. During this state, lightpropagating through the polymer material 173 strikes the sphere ofliquid crystal material 176, and will in general refract at the polymerliquid crystal interface because there will generally be a change in theindex of refraction of the (randomly ordered) liquid crystal materialand the polymer material. The layer 172 will then scatter light passingthrough. The light rays traced in FIG. 17A are shown transmitted throughthe layer 172, which would be the case for very light loading of liquidcrystal material in the polymer. In the more general case, lightincident on the panel would be as likely scattered backward as forward,and would likely be scattered isotropically in all directions.

In FIG. 17B, the PDLC panel 172 is shown operated in its transmissionstate, wherein an electric field is applied across the layer 172 byapplying voltage across the conducting layers 174 and 175. In this stateof operation, the electric field forces the liquid crystal molecules ineach sphere to line up parallel with the field, causing the index ofrefraction of the liquid crystal material to match the index of thepolymer material, thereby enabling the light rays pass through the layer172 without deviation or scattering.

In FIGS. 18A and 18C, a second illustrative embodiment of theelectrically-controllable light scattering structure 182 is shown in theform of a thin panel comprising a liquid crystal polymer material 183contained between a pair of spaced-apart transparent electricallyconducting layers 174 and 175 (e.g. ITO) having surfaces that have beeneither rubbed or coated with a molecular aligning layer such aspolyamide, well known in the CLC art. In this embodiment, the liquidcrystal material 183 is admixed with a polymer material, but unlike theembodiment shown in FIGS. 17A and 17B, the resultant material does notphase segregate. Instead, the linear liquid crystal molecules remainentangled in the polymer material.

In FIG. 18A, the electro-optical light scattering structure 182 is shownoperated in its reflection mode, wherein the crystal molecules (depictedas short lines) are lined up parallel with the conducting plates 174 and175 because, for example, the surfaces of the plates have been rubbed,causing the molecules to become internally ordered (e.g. aligned) suchthat incident light on the layer 183 is reflected as shown. Thismolecular ordering can be thought of as a “relaxed ordering” when noexternal electrical force field is applied thereto.

In FIG. 18B, the electro-optical light scattering structure 182 is shownoperated in its reflection mode, wherein an electric field is impressedacross the layer 183 by applyin a voltage across layers 174 and 175. Inthis state of operation, the molecules rotate to line up parallel to thefield and light, propagating parallel to the field, is transmittedthrough the layer 183 without scattering, reflection, or absorption.When the electric field is removed by disruption the applied voltagesource, the polymer acts as restoring force to rotate the molecules backto their starting relaxed ordering as shown in FIG. 18A.

In FIG. 18C, a third illustrative embodiment of theelectrically-controllable light scattering structure 182 is showncomprising liquid crystal polymer material 183 contained between a pairof spaced-apart transparent electrically conducting layers 174 and 175(e.g. ITO) having surfaces that have not been rubbed or coated with amolecular aligning layer such as polyamide, as in the embodiment ofFIGS. 18A and 18B. Thus there is no internal order imposed on the liquidcrystal material by rubbed bounding surfaces or layers, as in thestructure of FIGS. 18A and 18B. In FIG. 18C, the electro-optical lightscattering structure 182 is shown operated in its scattering mode,wherein there is no internal ordering created by rubbed surfaces orpolyamide layers, or an electric field created by an externally appliedvoltage. In this mode of operation, the liquid crystal materialnaturally tends towards lowering its internal energy by having nearneighbor molecules align with one another, but there is no long rangeorder. Thus the regions of material now scatter light randomly and,without the application an electric field, the light incident on thelayer 184 is scattered. When an electric field is impressed across thepanel of FIG. 18C, the molecules therebetween swing around to line upwith the applied electric field, enabling incident light to betransmitted through the panel 182 without scattering in a manner similarto that shown in FIG. 18B. This is the transmission mode of operation ofthe electrically-controllable light scattering device.

In FIG. 19, fourth illustrative embodiment for an electro-optical lightscattering structure (i.e. panel) is shown comprising an isotropicscattering material, such as a liquid crystal polymer, contained betweena pair of transparent glass panels. Each of these plates has an ITOcoating upon the glass plate surface, electrical terminals connectedthereto, and a polyamide layer applied upon the ITO layer.Alternatively, the ITO surfaces can be rubbed for intiating molecularalignment in lieu of the ITO layers.

In FIG. 19A, the electro-optical light scattering structure of FIG. 19is shown operated in its transmission mode, wherein no external voltageis applied (i.e. V=V_(off)). In FIGS. 19B and 19C, transmission andreflection characteristics for this mode of operation are shown,respectively. In FIG. 19D, the electro-optical light scatteringstructure of FIG. 19 is shown operated in its light scattering mode,wherein an external voltage V is applied across the ITO surfaces (i.e.V=V_(on)). In FIGS. 19E and 19F, transmission and reflectioncharacteristics for this mode of operation are shown, respectively. Aslight is transmitted when no external voltage is applied, and scatterswhen a voltage is applied, this structure is said to operate in the“reverse mode”.

In FIG. 20, a fifth illustrative embodiment for anelectrically-controllable light scattering structure is shown comprisingan isotropic scattering material, such as a liquid crystal polymer (madeusing a different polymer mixing ratio than used in FIG. 19), containedbetween a pair of transparent glass panels. Each of the plates has anITO coating upon the glass plate surface and an electrical terminalconnected thereto, but is not rubbed or coated with a polyamide or likelayer to ensure that there is no high order molecular alignment when noexternal field is applied.

In FIG. 20A, the electro-optical light scattering structure of FIG. 20is shown operated in its scattering mode, wherein no external voltage isapplied (i.e. V=V_(off)). In FIGS. 20B and 20C, transmission andreflection characteristics for this mode of operation are shown,respectively. In FIG. 20D, the electro-optical light scatteringstructure of FIG. 20 is shown operated in its light transmission mode,wherein an external voltage V is applied across the ITO surfaces (i.e.V=V_(on)). In FIGS. 20E and 20F, transmission and reflectioncharacteristics for this mode of operation are shown, respectively. Aslight is transmitted when an external voltage is applied, and scatterswhen a voltage is no applied, this structure is said to operate in the“normal mode”.

Such alternative embodiments of the present invention will beparticularly useful when a room is brightly lit at night, and a verysmall amount of light leaking from the inside to the dark outside maycompromise privacy.

Having described such alternative embodiments of the present invention,further modifications thereto readily come to mind.

For example, the electro-optical glazing structures described above canbe stacked and laminated together, in virtually any number or ordering,so as form composite electro-optical glazing structures having more thantwo optical states (e.g. four or more). Such electro-optical glazingstructures can be used to construct sophisticated window systems capableof providing complex levels of solar and/or visible radiation control.

Electrically controlled CLC-based smart windows of the present inventioncan be used in homes, schools, offices, factories, as well as inautomobiles and airplanes to provide privacy, brightness control, andreduce thermal loading on heating and cooling systems employed therein.

The electro-optical glazings of the present invention can be used tomake intelligent sunglasses and sun visors for use in a variety ofapplications. In such embodiments of the present invention, theelectro-optical glazing of the present invention is realized in the formof a pair of lenses which are mounted within a frame supportable uponthe head of its user, as in conventional eyeglasses or sun-visors. Theprogrammed microcontroller, battery, electromagnetic detector, batteryrecharging circuitry and optical state switching circuitry embodiedwithin the window frame shown in FIGS. 1A and 12B can be reduced in sizeand embodied within the ultra-compact sunglasses frame of thisillustrative embodiment of the present invention.

In yet another alternative embodiment of the present invention, theelectro-optical glazing structures of the present invention can bemounted before each LCD viewing panel within the shutter-typestereoscopic 3-D viewing glasses taught in International Publication No.WO 97/43681 by VRex, Inc., a wholly owned subsidary of Reveo, Inc.,which is incorporated herein by reference in its entirety.Advantageously, the application of the present invention thereto wouldprovide stereoscopic 3-D viewing glasses having several additional modesof operation, wherein the user could simply control electromagneticradiation in either a manual or automatic manner during stereoscopic 3-Dviewing or monoscopic 2-D viewing of displayed images (i.e. virtualworld viewing), or stereoscopic viewing of real world objects whilewalking, bicycling, jogging, sailing, or just lounging about in the raysof the Sun.

The electro-optical glazings of the present invention can be used inautomotive vehicles, maritime vessels, aircrafts and spacecrafts.

The modifications described above are merely exemplary. It is understoodthat other modifications to the illustrative embodiments will readilyoccur to persons with ordinary skill in the art. All such modificationsand variations are deemed to be within the scope and spirit of thepresent invention as defined by the accompanying Claims to Invention.

What is claimed is:
 1. An electro-optical glazing structure havingreflection and transparent modes of operation for selectively reflectingand transmitting electromagnetic radiation without absorption,respectively, said electro-optical glazing structure comprising: anelectro-optical panel having first and second optical states ofoperation; a composite infrared (IR) reflective polarizing filterstructure of electrically-passive construction, mounted to saidelectro-optical panel; and an optical state switching mechanism forswitching said electro-optical panel to said first optical state ofoperation in order to induce said electro-optical glazing structure intosaid reflection mode of operation, and for switching saidelectro-optical panel to said second optical state of operation in orderto induce said electro-optical glazing structure into said transparentmode of operation, wherein electromagnetic radiation within a firstprespecified bandwidth falling incident upon said electro-optical panelis reflected from said electro-optical panel without absorption whensaid electro-optical panel is switched to said first optical state ofoperation, and wherein electromagnetic radiation within a secondprespecified bandwidth falling incident upon said electro-optical panelis transmitted through said electro-optical panel without absorptionwhen said electro-optical panel is switched to said second optical stateof operation.
 2. The electro-optical glazing structure of claim 1,wherein said composite IR reflective polarizing filter structurecomprises: a left-hand circularly polarizing (LHCP) IR reflectivepolarizing panel of electrically-passive construction, and a right-handcircularly polarizing (RHCP) IR reflective polarizing panel ofelectrically-passive construction.
 3. The electro-optical glazingstructure of claim 1, wherein said electro-optical panel comprises: afirst electrically-passive cholesteric liquid crystal (CLC)electromagnetic radiation polarizing panel; a secondelectrically-passive CLC electromagnetic radiation polarizing panel; andan electrically-active π-phase retardation panel interposed between saidfirst and second electrically-passive CLC electromagnetic radiationpolarizing panels.
 4. The electro-optical glazing structure of claim 3,wherein said first and second electrically-passive CLC electromagneticradiation polarizing panels totally reflect without absorptionelectromagnetic radiation having a left hand circularly polarized (LHCP)state and a wavelength within said first prespecified bandwidth whensaid electro-optical panel is switched to said first optical state ofoperation, wherein said first and second electrically-passive CLCelectromagnetic radiation polarizing panels transmit without absorptionelectromagnetic radiation having either a right hand circularlypolarized (RHCP) state and/or a wavelength outside said firstprespecified bandwidth when said electro-optical panel is switched tosaid first optical state of operation; and wherein said first and secondelectrically-passive CLC electromagnetic radiation polarizing panelstransmit without absorption electromagnetic radiation having either saidLHCP state or said RHCP state and a wavelength within said secondprespecified bandwidth when said electro-optical panel is switched tosaid second optical state of operation.
 5. The electro-optical glazingstructure of claim 1, wherein said electro-optical panel comprises: afirst electrically-active cholesteric liquid crystal (CLC)electromagnetic radiation polarizing panel; a second electrically-activeCLC electromagnetic radiation polarizing panel; and anelectrically-passive π-phase retardation panel interposed between saidfirst and second electrically-active CLC electromagnetic radiationpolarizing panels.
 6. The electro-optical glazing structure of claim 5,wherein said first and second electrically-active CLC electromagneticradiation polarizing panels totally reflect without absorptionelectromagnetic radiation having a left hand circularly polarized (LHCP)state and a wavelength within said first prespecified bandwidth whensaid electro-optical panel is switched to said first optical state ofoperation, wherein said first and second electrically-active CLCelectromagnetic radiation polarizing panels transmit without absorptionelectromagnetic radiation having either a right hand circularlypolarized (RHCP) state and/or a wavelength outside said firstprespecified bandwidth when said electro-optical panel is switched tosaid first optical state of operation; and wherein said first and secondelectrically-active CLC electromagnetic radiation polarizing panelstransmit without absorption electromagnetic radiation having either saidLHCP state or said RHCP state and a wavelength within said secondprespecified bandwidth when said electro-optical panel is switched tosaid second optical state of operation.
 7. The electro-optical glazingstructure of claim 5, wherein said first and second electrically-activeCLC electromagnetic radiation polarizing panels totally reflect withoutabsorption electromagnetic radiation having a right hand circularlypolarized (RHCP) state and a wavelength within said first prespecifiedbandwidth when said electro-optical panel is switched to said firstoptical state of operation, wherein said first and secondelectrically-active CLC electromagnetic radiation polarizing panelstransmit without absorption electromagnetic radiation having either aleft hand circularly polarized (LHCP) state and/or a wavelength outsidesaid first prespecified bandwidth when said electro-optical panel isswitched to said first optical state of operation; and wherein saidfirst and second electrically-active CLC electromagnetic radiationpolarizing panels transmit without absorption electromagnetic radiationhaving either said LHCP state or said RHCP state and a wavelength withinsaid second prespecified bandwidth when said electro-optical panel isswitched to said second optical state of operation.
 8. Theelectro-optical glazing structure of claim 1, wherein saidelectro-optical panel comprises: a first electrically-active cholestericliquid crystal (CLC) electromagnetic radiation polarizing panel; and asecond electrically-active CLC electromagnetic radiation polarizingpanel adjacent said first electrically-active CLC electromagneticradiation polarizing panel.
 9. The electro-optical glazing structure ofclaim 8, wherein said first electrically-active CLC electromagneticradiation polarizing panel totally reflects without absorptionelectromagnetic radiation having a left hand circularly polarized (LHCP)state and a wavelength within said first prespecified bandwidth whensaid electro-optical panel is switched to said first optical state ofoperation, and wherein said first electrically-active CLCelectromagnetic radiation polarizing panels transmits without absorptionelectromagnetic radiation having either a right hand circularlypolarized (RHCP) state and/or a wavelength outside said firstprespecified bandwidth when said electro-optical panel is switched tosaid first optical state of operation; wherein said secondelectrically-active CLC electromagnetic radiation polarizing paneltotally reflects without absorption electromagnetic radiation havingsaid RHCP state and a wavelength within said first prespecifiedbandwidth when said electro-optical panel is switched to said firstoptical state of operation, and wherein said second electrically-activeCLC electromagnetic radiation polarizing panels transmits withoutabsorption electromagnetic radiation having either said LHCP stateand/or a wavelength outside said first prespecified bandwidth when saidelectro-optical panel is switched to said first optical state ofoperation; and wherein said first and second electrically-active CLCelectromagnetic radiation polarizing panels transmit without absorptionelectromagnetic radiation having either said LHCP state or said RHCPstate and a wavelength within said second prespecified bandwidth whensaid electro-optical panel is switched to said second optical state ofoperation.
 10. The electro-optical glazing structure of claim 9, whichfurther comprises: a electromagnetic-sensor mounted on said windowframe, for sensing electromagnetic conditions; a battery supply mountedwithin said window frame, for providing electrical power; aelectromagnetic-powered battery recharger mounted within said windowframe, for recharging the battery supply; electrical circuitry mountedwithin said window frame, for producing glazing control voltages forswitching said first and second optical states of operation; and aprogrammable micro-computer chip mounted within said window frame, forcontrolling the operation of said battery recharger and said electricalcircuitry, and the production of said glazing control voltages asrequired by a radiation flow control program stored within saidprogrammable microcontroller.
 11. The electro-optical glazing structureof claim 1, which further comprises: a window frame for mounting saidelectro-optical panel within a house or office building, or aboard atransportation vehicle.
 12. An composite electro-optical glazingstructure which comprises: a plurality of said electro-optical glazingstructures of claim 1, stacked together as a composite electro-opticalstructure, and wherein said composite electro-optical structure has morethan two said optical states of operation which permit complex levels ofelectromagnetic radiation control.